To start I want to be clear if you just want to have fun on Oscar night and don't care about winning then that's it probably be more fun for you if you go into Oscar night cold. Second I'm assuming any one reading this is an amateur if you read Oscar sites or happen to write one you probably don't need my help.
Do Your Homework- Make sure to read creditable Oscar sites Award Circuit,Awards Daily and Never Too Early Movie Predictions are all very good at not just predicting but explaining the Oscars. Take more than 5 minutes to read the commentary and explanation.
Don't Copy and Paste-First off it cheating if you just take all their (the sites) predictions. If you agree with most of their predictions more than the reason than they said so then that's fine. But Remember there not always right it's the unknowns that can call the upsets don't be afraid to shake it up when it a close race or hard to call.
Don't be swayed by Personal Opinion/Knowledge- It always tempting to look at an Oscar prediction sheet and say hey I know that guy I'll predict him . A lot of Oscar predictors are going to swayed by seeing Meryl Streep or Brad Pitt name on the list and just picking it for that reason alone . Also if you really like a movie with zero chance of winning don't pick it. I don't care if someone thought Extremely Loud and Incredibly Close is the best movie of the decade it isn't going to win so don't pick it.
Stick to Your Picks- If you so adsorbed with the ceremony that your changing your picks last minute then one you'll kick yourself if you change it too the wrong thing and two there a good chance you'll change it too the wrong prediction. A good rule of thumb is the favorites almost always win so pick the favoritism(minus a few).
Pick A Upset or Two- Every year there will one or two upsets so you should predict a upset but remember there is a time and a place to predict a upset. Don't go predicting Jonah Hill in the supporting actor category().