I hope this helps..

• Do a complete chain as you can at early stages (smaller sparks).
• Sparks need space to move around, so try to eliminate in-between sparks.
  (Meaning.. Do irregular "any direction" tap tap to give space. Don't always go clockwise or counter-clockwise.)
• Eliminate bigger sparks first, like the big red things (don't know what's the name. lol) or peanuts.
• Always use "2X" in your chain to give double points.
• If you see "Explosion Special".. Do a complete chain if you can, then blow everything up. lol
• Don't get distracted when you use "Speed Slower Special". The sparks are moving still, even though its slower. Keep your speed.
• Pause the game whenever you need to do something else. lol. It will give you fresh feeling when you resume it.
• Don't be greedy

Have fun playing geoSpark..