Stick to the defined route as much as possible - leaving it will only slow you down.
Don't waste your special items unnecessarily, as they could be the difference between success and failure.
Upgrade your moles whenever possible, as improving their stats (Speed, Acceleration, Strenght) can make it easier to achieve a more impressive score.
Try grabbing the large clear gems that occasionally appear. Once you've picked up three of these, you'll be placed inside a giant robotic suit which is invulnerable and very fast. It lasts for a few seconds, but it's a great way of grabbing a huge stash of gems and breaking distance records.
Grab every gem of the same color in a single line as it will give you a speed boost that can be increased with further collections.
Green Shield - Gives you a rocket blast through all scenery and speed-inhibiting soil. Will also take out enemies, and its relatively gentle pace allows you to grab a decent chunk of gems at the same time.
Hammer - Smashes anything in front of you, be that a rock or an enemy. Most useful whenever the warden's getting near and you need to get away at all costs.
Red Shield - Our favorite upgrade. Picking this up encircles your mole with a powerful spinning ring of spiked steel that eats through anything he comes into contact with.
Bomb - Self-explanatory! As you can only drop bombs behind you, we like to save this one up for whenever the prison warden's on our tail. Just drop it behind you and let him clatter into it.