After checking if you have a Mac that will be able to run Mountain Lion, the next thing (well not really, you should run Software Update and backup your files first) is to check if your software will work with the new cat. Roaring Apps, has a list of common software on the Mac, and will tell you if it will work or not, or if it runs with some bugs. Last year, when we made the upgrade to Lion, I told everyone to check this wiki, it has very useful information and it’s updated as more people report on the software and how it works with the new operating system.
Apple said that Mountain Lion would ship in July, and last year they released Lion the day after the Quarterly Financial Conference Call. So it is a good guess the same will likely happen this year. Check the list before upgrading. You don’t want to find out that an app on which you rely for daily work, will not run on Mountain Lion, after making the jump. Better safe than sorry.