The Illinois CPA Society has come up with six tax recommendations for younger filers:  take full advantage of available deductions and credits (such as the first-time homebuyer credit, child credit and lifetime learning credit). It is important to make sure that you have appropriate documentation,  e-file for faster refunds (but avoid like the plague any refund anticipation loans),  file a 1040A or 1040EZ rather than Form 1040 if you qualify and don't miss deductions or credits by doing so,  pencil in the work before filing to avoid errors (you don't want to hear from the IRS in July),  if you think that you might qualify for a deduction or credit but aren't sure how to get it, read IRS material such as form/schedule instructions or Publication 17
or sign up with a tax pro (such as an enrolled agent (EA) or certified public accountant (CPA)),  make sure that you acknowledge all income sources, especially if you receive Forms W-2 or 1099. Again, if you end up needing to file Forms C (business), F (farm) and/or SE (self-employment), it might well be time to sign up with a tax professional.
All the hints given by the Illinois CPAs are good, and not necessarily just for filers under 30. Two added things to consider:  schedule your W-4 to keep your refund low (the IRS gets your money free for more than a year in some cases if you have a large refund). If saving is hard for you, have your employer withhold a small amount each month to invest in a conservative mutual fund or savings account (most but not all will do this),  do not procrastinate. You get your refund faster and find professional help easier to get (and less grumpy) if you file by the middle of March.