As an acting, there are going to be a lot of auditions, a lot of unsuccessful ones, but why have it be a stressful or bad experience. Have fun with each one and give a reason to have the casting director call you back again for other parts. Even though I don't always get the part, casting directors do seem to like me and do ask for me by name. Maybe it is because I make an audition fun for everyone.
For the latest audition I did yesterday (for a television series), we were supposed to come in Western costume. I recently moved and didn't bring all my costumes with me so I had to quickly hit the second hand stores for a costume. I managed to put together a western-ish costume. Sadly I couldn't find a cowboy hat, except for a dorky straw one. I got it and decided to have fun with it. When I did my "slate", introduction of myself, I did a joke about someone stealing my good cowboy hat and getting stuck with the bad one. Then I ditched the hat and did fine without it, looking Western enough I believe in a long sleeved dark shirt and black vest and jean and cowboy boots (although the boots weren't on camera, it still helps to get in to character to wear the right thing). The casting director was really happy with the few lines I did for a small part, she had me read for a bigger part. That was a very good sign.
Getting a new part is a challenge at the last minute. I'd worked all day on a couple of lines (saying them at everyone slight opportunity in regular conversation - thankfully my wife didn't get too annoyed). Suddenly I had four new lines to do. They offered me a few minutes to prepare so I took it. I went out in the hall and went over my new lines. Then I jumped in and did it. Amazingly I got the lines right on the first try.
A few things I learned this audition (always try to learn something new from each audition):
1. Be prepared for changes. Practicing memorizing something quick is a good skill.
2. If you get more than one chance at lines, try to make them better with each try by doing something a little different. The casting director was very happy with my final try.
3. Try to stay in character for most of the audition. I forgot to do this at one point and probably ruined one of the takes. Thankfully I got another.
4. Remember that the casting director isn't the final word. They are recording you for a reason. Someone is going to decide if they want you or not based on your camera performance so make your on camera time count.
5. It never hurts to say thank you. I'm going to send some thank you emailed to the casting directors now.