So far I've been doing pretty badly.  I'm having trouble beating my high scores in deadline, king and evolved and am hoping someone has some tips I could use.

For King, it's good to clear a path to the next circle, and collect a lot of geoms on the way. You definitely want to focus on the snakes when they appear. I haven't played deadline or evolved as much, so I can't give you many good tips.

Deadline: Charge full speed for the first 30 seconds, then concentrate on staying alive. So use your bombs.
King: As he said, clear a path to the next circle and make sure to take out snakes
Evolved: Go in a circle and fire behind you, and make sure to use all your bombs before you die completely

Deadline:  Early on kill enemies and collect Geoms as quickly as possible just going straight towards the enemies and trying to clear out each wave as quickly as possible so that the next will appear (yes very obvious).   Using bombs is better then dying,  the longer you stay alive the more waves of enemies will appear faster it seems.  Once you get a steady flow of enemies go back and forth shooting in front of you along the bottom third of the screen collecting Geoms as you go.  This is a much better strategy then the circular pattern that worked so well in the original.   If you get a break shoot towards the upper half of the screen and pick up points,  but the best way to get geoms and stay alive is a left to right pattern along the bottom portion of the screen or top,  but generally you want to focus on increasing your multiplier as quickly as possible  over killing the maximum amount of enemies for the first 2 and a half minutes.   After that point just go wild and kill as many enemies as you can and forget about the Geoms.  

Waves:  With the first 4 or 5 sets of waves,   just find their location and try your best to take them out in a nice string so you can collect their Geoms quickly.  After that point,  pick a corner (lower right for example but not to close to the edge) of the board that you are comfortable with and make that your base for the rest of the proceedings.   If you are in a corner you can see the spawns for two different directions and can only get surprised from two other.  Plus if you are in the bottom right for instance,  you do not have to worry about any ships going left to right in the upper half of the screen,  or any ships going up and down on the left side of the screen.  Any ships that spawn near you, take care of them and if you hear a spawn off screen then shoot in one of the two unknown directions they are coming from to try and increase your chances of not getting surprised.   Any break you get shot a spread pattern at the opposite corner of your ship to pick up kills and points.   If you are "for example"  in the lower right corner and you clear out a big chunk of enemies along the bottom part of the screen,  then go for those geoms if you think it is safe.   Once gates start appearing and you have a clear path, go for them.  I have no idea what the math is behind the scoring involving enemies destroyed by gates but they seem to shoot your score up more then anything else. 

"Deadline:  Early on kill enemies and collect Geoms as quickly as possible just going straight towards the enemies and trying to clear out each wave as quickly as possible so that the next will appear (yes very obvious).   Using bombs is better then dying,  the longer you stay alive the more waves of enemies will appear faster it seems.  Once you get a steady flow of enemies go back and forth shooting in front of you along the bottom third of the screen collecting Geoms as you go.  This is a much better strategy then the circular pattern that worked so well in the original.   If you get a break shoot towards the upper half of the screen and pick up points,  but the best way to get geoms and stay alive is a left to right pattern along the bottom portion of the screen or top,  but generally you want to focus on increasing your multiplier as quickly as possible  over killing the maximum amount of enemies for the first 2 and a half minutes.   After that point just go wild and kill as many enemies as you can and forget about the Geoms.  

Waves:  With the first 4 or 5 sets of waves,   just find their location and try your best to take them out in a nice string so you can collect their Geoms quickly.  After that point,  pick a corner (lower right for example but not to close to the edge) of the board that you are comfortable with and make that your base for the rest of the proceedings.   If you are in a corner you can see the spawns for two different directions and can only get surprised from two other.  Plus if you are in the bottom right for instance,  you do not have to worry about any ships going left to right in the upper half of the screen,  or any ships going up and down on the left side of the screen.  Any ships that spawn near you, take care of them and if you hear a spawn off screen then shoot in one of the two unknown directions they are coming from to try and increase your chances of not getting surprised.   Any break you get shot a spread pattern at the opposite corner of your ship to pick up kills and points.   If you are "for example"  in the lower right corner and you clear out a big chunk of enemies along the bottom part of the screen,  then go for those geoms if you think it is safe.   Once gates start appearing and you have a clear path, go for them.  I have no idea what the math is behind the scoring involving enemies destroyed by gates but they seem to shoot your score up more then anything else. "