Its all about mastering the slide boost. Also getting hit with a shell, getting ink in your face or whatever is much worse if you let those things phase you. If you get a banana peel you can us it as a back shield if you push the weapons button and just hold it.
Kart games are great and fun. Play some singleplayer stuff. Can't wait to play MK8Deluxe. I've played sonic all star racing on the PC and it's fun and mario kart/crash kart idea copy.