Is there a good flexibility and balance routine you'd suggest for a martial artist? I do karate, and my style doesn't use high kicks.
[ame="https://www.youtube.com/watch?v=QrVgpDOLlgM"]How To: Kettlebell Goblet Squat - YouTube[/ame] one of the best ways to develop leg mobility (nevermind how deep he goes, think of it as a goal to strive towards).
Not designed for MA-ists per se, but copy ballerinas' balance/flexibility routines. It works. Here's one aimed at beginners: [ame="https://www.youtube.com/watch?v=5NgRcaKdrAU"]Flexibility Stretches For Dancers, Cheerleaders & Gymnasts, Beginners Exercises Routine - YouTube[/ame] I haven't done much yoga, but it looks useful to me.
Called developpe in ballet. [ame="https://www.youtube.com/watch?v=m4A6PLeGIB4"]Insight: Ballet glossary - développé - YouTube[/ame]
I'd like to improve in situations where the ground isn't level. I'd also like to be able to control my kicks more. Avoid being tackled. General stuff.
Exercising on an unstable surface (Bosu ball, stability board etc) might help. I mean, what situations are you referring to? Again, you're a bit too ambiguous. Control, as in hitting a target at full speed without missing? Or control, as in tidying up your technique so it looks less "sloppy"? Or control, as in being able to hold your leg up in the air? Don't play rugby. Failing that, go to a wrestling class and learn takedown defence. You need to avoid "general" questions if you want useful advice.
Practice kicking on uneven ground. Do it a lot. That's the only thing that will build the necessary proprioception, balance and stabiliser muscles.