It depends on what kind of plot holes you're talking about. Do you mean trying to fix all types of plot holes while writing the story so that you have a "perfect" script to work from when you start drawing (assuming you're working on a comic story)? Or are you talking about fixing plot holes in a story you already started working on (and posting) where you realise there are things you haven't thought through well enough?
This.
But one advice in general: when revising, try not to get too attached to individual story elements, such as that one cool quote or that amazing scene. Sometimes those things need to go in order to make the story work better as a whole. I think writers of all level* have this problem; even though an accomplished writer may know what they're doing, it's still emotionally tough to cut out some of their favorite parts.
*though not necessarily every single writer... just SOME writers across all levels. I know some writers are good about editing their own work ruthlessly.
Some general advice I can give is to have a partner/confidant and go over the story with them. I work with two other people and they have seen through things that I haven't, allowing us to fix issues in the story together that I wouldn't have noticed otherwise. Having more eyes on something always helps.
Definitely having a friend or confidant to work with helps with plot holes and inconsistencies.
I pushed a concept onto a friend and he helped to polish it until it was something really clear, something that could, after decent storytelling is done, can be grasped simply.
Agreed with @keii4ii and @ingunn that it really depends.
If plot holes are a large problem I think the best general advice is to finish your work as a rough draft and throw it into the fire with a group of friends. I do that with all of my scripts, where I borrow from TV and we do what's called a live read through. Friends take parts, I do the narration and we go. After each act break we stop and work through what stood out to us a problematic. Oftentimes this really helps with dialogue too. Monologing is not in the best interest of your readers, and frankly it gets old. So they'll help me figure out where to shorten it, and when to expand upon it. Half the time if they're reading aloud and get tripped up, then I KNOW I have to change it.
I appreciate the comments and tips. I was asking for precaution. I am currently working on just the script. I have no problem editing my work. I just want to avoid them as much as possible.
This has helped me a lot too, when I've done it. Plus, it's super fun. And embarrassing.
Probably the most helpful thing I do to help eliminate plot holes is to keep a running list of questions about my work. I go back and re-read my stuff periodically, and then I always make sure to think about what's going on. If something might be ambiguous or a character's motivation is shallow or something doesn't add up, I write that down on my list. If anybody asks a question about the world or characters or story, I write the question down. And every day before I begin writing, I read through the list. In my NaNoWriMo novel a few years ago, I had like five pages of questions by the end of the month. By keeping the questions constantly in front of me, my brain is always working on it and I've been able to fix a lot of mistakes.
Also, one of my favorite parts about writing comics I can't redraw is the fact that I have to roll with my mistakes. You can't just ignore them, you have to use them in the story. I really love webcomics.
Personally, I think you should start making a story by seeing where you want it to begin and end, and fill in the rest in the middle. Plot holes can come from lack of explanation on a certain area. While it works with some stories, say for example Over the Garden Wall, since it takes place in a sort of mystery and fantasy-like setting. However if you are unable to explain how a certain thing happened in your story, or why it happened, that may lead to confusion with the audience. I myself am not the greatest writer, but we all are learning from each other. Look and you story and make sure it makes sense to you. Get some people to pitch in and give you advice if you are ever confused. Read and reread your work so that you make sure everything can come to full view for the audience. If you want to leave a sense of mystery, than have your story open to various interpretations. It's all about the comparison of how you perceive your story to how the audience perceives it.
I am probably the worst person to ask advice for but there you go I tried.
I basically agree with what everyone here's been mentioning. Having someone else go through your work is helpful for so many reasons - they can often point out inconsistencies that you've overlooked yourself. Other than that, I would recommend that you do the necessary amount of research you need to write your story. And it can be VERY difficult to know what the right amount of research is, and it depends a lot on the type of story you're writing.
I hope you at least feel accepted in the tapastic community? What I can think of right now that could be helpful for you is NaNoWriMo2. It's only a few weeks away, and there are usually local events2 where people from the same region can meet up and write with other participants. I've never participated in one of those, so I'm not sure if people give each other feedback - the point is to reach a word count, so people mostly just write together I guess. But you'll get to hang out with people with similar interests, and maybe some of them would like to start a writers group 
Here's something I do.
I write 'Behind the action' scenes. These are just quick dialogue scenes that will never appear in the comic, but nonetheless happen alongside the plot. I sometimes act them out in my head when I go for a walk. An example might be, the characters are stuck in a dungeon, trying to figure a way out. Well, you can write a scene of the villain and his henchmen talking about their plans for the prisoners.
Once you've done enough of these, you'll have a much better idea of the big picture, and any plot holes should stick out like a sore thumb. I find writing these scenes really helps to cement each and every character's motivations and personalities. Often you'll uncover some important element about a character that you can then allude to in the actual comic. Basically, what you're trying to avoid is your readers asking questions like "why didn't he just do this?"
Also, just be aware that if you're writing fantasy or sic-fi, it's unlikely you'll be able to wrap your story up as tight as a drum. Even the most popular stories have funny little plot holes, and that's okay, because there's an expectation of drama and suspension of belief. 'How it should have ended' on youtube is testament to that.
And then there's always the excuse that your character maybe just didn't think of this or that when they should have. You can get away with that if by making your characters realistically fallible.
These are actually some of the best people to have looking at your work. Otherwriters are great, and they can really help with technical stuff, but general audiences that'll be reading your comic are more than likely not writers. Pretty much all of the people I have doing our read through on rough scripts aren't writers by trade at all.
If your friends are distant and busy, schedule a skype call once you have the draft finished. More than once I've done a read through that way too. Ask them to help and offer a day in the future you can all agree to chat on. Then narrow it down to time.
From there it's all about making sure that they know WHAT you're looking for. I usually tell my folks, "Okay, if something jumps out at you as confusing, or nags at you, doesn't make sense or has a grammatical error (outside of obvious accents etc), mark it and lets talk through."
Big plot holes will show up. Text you've written will be hella cliche in some parts. In fact it MAY suck and that's perfectly okay. The first part of getting something good is finding it's flaws. If you find a lot of them, just think how much BETTER the next script will be!
But first...you need your script. <3
Good luck, bb!
I always talk to myself out loud about the plot and that way I found pretty big plot hole in my story :v
But seriously, I find this a good way.
Oh and the script is important, personally I prefer to write it than draw sketchy panels on paper.
Sometimes the only way to get away from plot holes is to distract the audience from them :B ive never seen a story without a plothole to be honest, but this is human nature, after all hindsight is 20/20 and not everyone has perfect vision. So often you let it go if your distracted enough and enjoy the story well enough that the plot hole isnt horribly distracting.
