Hint - Double Score Zone Exploit
Double score zones allow players to gain double the credits from studs. Because of that weird effect, you can exploit it by killing your partner (2 active players only) and taking his money (and vice versa). While you lose a set amount of money, you also gain double that amount because of the double scoring effect.

Hint - First Game Data Carry Over
There is an extra that can be bought in the shop if you have LSW1 data available. You can do this import only once, so only characters and vehicles you unlocked from the first game are introduced into the Free Mode for the second.

Hint - Self Destruct Extra
Just thought I'd mention the self destruct isn't a completely useless extra. Though blowing up your droid may seem like a bad idea, it is worth noting you don't lose studs (from the act of self-destruct). This means that you could blow up to prevent losing studs from falling, or you can send your droid, which is usually ignored by enemies, into the middle of a bunch of them, and boom. If you opt for the invulnerability extra, it's kinda pointless entirely, but it's an option open to other players.