There is a great way to save your various takes (including rough "scratch tracks") or unused note sequences in Propellerheads Reason 4, which is referred to as its Track Lanes. Essentially, as you are beginning to structure a piece of music into the various parts (intro, verse, chorus, and bridge), you can easily audition arrangement ideas over an 8- or 16-bar loop simply by muting and unmuting the various Track Lanes as your loop plays.

It's also a good idea to build up a library of custom Groove Patches for use in Reason's ReGroove mixer. This way, even if you don't end up using a particular groove in your final product, you won't have to start from scratch. Plus, with a little help from audio editing software and a copy of ReCycle!, these can actually be extracted from your favorite songs and then applied to your own. And if you're having trouble getting parts with different types of grooves to sit well together (usually because one or more hits are clashing with each other), try applying these grooves permanently to the clips. In this way, you will be able to match up only the offending hits, leaving all the other note events intact. You'll be surprised how much time this will save when working out various arrangements.