I haven't read to many mangas yet, but Katsuhiro Otomo is one on my faves. I just got the colored manga version of Akira a few days ago and the amount of detail in the backgrounds and the way he blends a japanese and western drawing styles for the character designs are truly inspiring. It makes me really glad that I have taken upon myself the burden of learning to draw backgrounds, because it can look so damn good and I want to strive to come closer that ideal. I also really love the dynamic of his composition.
In the same vein I also really like Masamune Shirow, even though I should mention that I prefer his older pre digital drawing style. That man can use his traditional materials so well and it gives his colored drawings this unique "gritty" look, that I really love. He also give a good dose of background porn, so that's always appreciated ^^
Aside from that...hm... the guy who did Death Note? Takeshi Obata? I really respect how clean the drawings in it look. Reproducing a clean style with the characters staying consistently on model is really hard and he does that really well.
Those three mangakas just have great stories and great art, so there is lots to love from me, even though those are not "secret tips". ^^ I also love the art in Battle Angle Alita, but the story has gone a little downhill.
Special shoutout to Elfenlied and Lynn Okamoto. I don't really like the story and the drawings are pretty bad in places, but it kinda gives me hope to see that people can still love a story while the art quality is still developing ^^