can you guys give me any tips on performing a freestyle?
Bring your best stuff, and know it well. Try not to mess up.
In case you do mess up (which you shouldn’t because you’ve gotten your tricks SO smooth at this point) bring an extra yoyo. Put that extra yoyo by your feet at center stage and open the slipknot wide so you can get it on your finger easily.
Pick music that fits your style.
Have fun!!! Someone having fun is way more engaging than someone staring at their hands.
To add to the post above ^, if you mess up try to make it look like you did it on purpose.
Adding on to j. lev and theyoster109’s ^ 
I practice my freestyles in 15 second increments. That way all I have to do is develop twelve 15-second combos instead of one 3-minute freestyle (in my head it makes it less daunting). Unfortunately my planning stage starts typically within the week that I know I’m going to be doing a demo/freestyle so when I get on stage I usually loose track after the first minute and have to improvise as I remember what I wanted to do.
Some people will name those 15 second combo’s and memorize them as tricks. After that they simply have to memorize twelve different tricks in order and then as time goes on they can polish their freestyle, moving those twelve tricks around or tweaking them so they will fit their music better. After a few contests you’ll be able to start figuring out what gets you higher scores and better crowd response (typically by watching video’s of your freestyles and listening for hints) and it will allow you to develop a truly awesome routine with amazing potential.
Best of luck, I’d love to see what you end up coming up with
Pace your self… You dont want to rush through everything and then have 15 seconds left going… Wait… What am I going to do now?
If you mess up, only retry once or twice, you dont want to take up too much time so that you miss out on your ending tricks…
Going on with both of those I suggest you plan out enough tricks to make up a 3 and a half minute freestyle, so incase you do rush through, or you miss alot of big tricks, and are left with some time, you have a few more tricks to toss out
First Make a list of tricks you get on your first, second and third try then put the all together (only use a few that you get on your third try, judges like it when you take risks). Try to do tricks like slack or lacerations separate than tricks like boingy boing and sea sick.
Then when your done pick a popular song and do it to the rhythm of the song.(Watch some Chinese freestyles to see what I mean) 
[Tips for practicing at home]
When I practice freestyles what usually happens is first I’ll pick a song, then “choreograph” it to that.Plan it in 10-20 second regiments or however you feel comfortable doing the tricks in the freestyle.If it’s for a first freestyle just focus on getting up there for your first time with a plan, make sure all of the tricks in your freestyle are dialed. If they’re not get them to where you hit them every time off stage, that way even if you’re nervous the tricks will be embedded in your mind, rather then having to wing the entire thing (which I have done, and it really isn’t good.)
[Tips for when you arrive at the contest]
Get to the contest before anything notable happens (9:30 is a safe bet).Take a step onto the stage and look out onto the audience, you’ll probably see a bunch of kids, their parents, and some people you have seen post a video, or seen a picture of. These are the people standing in front of you watching your performance. There’s really not much to be worried about besides landing your tricks to do the best you can.
[Tips for before your performance]
Do some jumping jacks, sing a song, distract yourself until you’re called on to stage. Use some Talcum or baby powder, or if you can find a POWDER spray deodorant, that is the best for sure. Keep pep talking yourself, maybe have a group of friends you can look to on the side of the stage as support in case you get overwhelmed by all of the people looking at you on stage.
[Tips for on the stage]
Smile, when you’re comfortable, everyone is more comfortable. Place your yoyos down in the center of the stage in front of you with the loops open (in case you tangle a yoyo, you want to replace it fast!). Take a few deep breaths and just realize that you have done this many times before, and you can do this!
[After the freestyle]
The part I always mess up on, when everyone claps for you take a bow, even if it feels weird, it gives the freestyle some closure, even just wave to the crowd is fine, as long as you acknowledge they’re there. And finally congratulate yourself, you made it through your first freestyle!
Well i tried to help.
Bergy.
Think nothing of it, just have fun. Make sure you smile and look at the crowd. Don’t sit there staring at your yoyo while you’re doing tricks.