Well first of all, your going to want to be in shape. I dont know what your skill level is, i assume your trying out for high school. Some good technical drills are foot work drills. I have played for 10 years and what i have learned is that without a good touch, your not going to do well at all. Some good drills are simply juggling and kicking a ball against a wall as well as just doing to taps, scissors, and pull backs. Look up videos on YouTube, there are tons! To simply summarize this, FIRST TOUCH IS KEY! I hope this helped, good luck!
Some good soccer drills to practice for tryouts include dribbling the ball around cone and pass relay race and practice the tick tock game. You need also to practice dribbling across a square which is good for warm-up and perform the lofted pass game. Check out http://www.soccerhelp.com/Soccer_Drills.shtml.
One way to good touch, going off the first answer, is to sit down and keep your foot on top of the ball and your foot will get used to being that high off the ground to trap the ball. And if you want better skill, look up on YouTube soccer skill drills and soccer turns. I did those everyday for high school soccer and I came a long way.
Try a cool web site called http://www.thesoccerinfo.net , it has a youth, AYSO, also High School, and Coach section for soccer drills, very helpful, plus the search bar let's you put in any topic and finds it for you on the site with many search results, it's cool , we use it all the time