There's a lot of confusion out there about this whole deal of having a "handicap" in golf. Many sandbaggers will lie about their handicap, but that's another story. Let's deal with how you actually figure your handicap, OK?
You must record each score you have in your last 20 rounds of golf. Each score must be adjusted for your assumed handicap. i.e., if you are a 0-10 handicap, the most you can take on any one hole is a double bogey (two over par). If you are a 10-20, the most you can take is a 7 on any hole. If you are over a 20, you should probably find another hobby.
Now that you have your adjusted scores for the last 20 rounds, you must do the math. Take your score for each round and subtract the course rating. Any good golf course will have a course rating. Then multiply the resulting number by 113 (the standard slope rating) and divide the result by the actual slope rating of the course. Take the average of the best 10 of your last 20 resulting numbers.
This is your handicap (after you've multiplied the total by .96; don't ask questions, just do the math, OK?) , and you should never be ashamed to both admit it and use it to make wagers with strangers. If you find they have lied about their handicaps, break their thumbs in a painful manner.