Has it been a while since you last attended Mass or are you planning to check it out for the first time? The Mass Kit is a resource that will teach you everything you need to know about the Mass so you don't feel left out.
For all the prayers and responses used during Mass, as well as a side-by-side comparison of the new Mass parts, check out How To Go To Mass.
Remember, in order to receive the Eucharist at Mass, you must have confessed any mortal sins you've commited. Check out How To Go To Confession for more information.