It really depends.
If it's happening at the beginning of a new chapter, you could ease into it by making it clear that your characters have experienced the time between now and the previous scene... It could be as simple as their hair could be longer or they've clearly aged if it's been years of time between scenes. You might not have to not call too much attention to it as long as you give your readers time to notice the age gap before diving back into the plot.
If it's something like, they've made a plan and now they're in the middle of initiating it, you could start with someone saying "everyone ready?" and then the next panel establishes the secret base they are infiltrating, with guards and spotlights. And the panel after that could be someone tinkering with the grate on an air vent as they realize they've hit a snag in their plan...
Really, you could get really creative with it. Watch Paprika if you want to see mind-blowing shifts... (Although it's rated R... just a heads up on what you'll be getting into.)
In the end though, yes, the comments above have perfectly valid points. A simple 'two days later' panel does the job. 