I mostly just group things really well and manually organize object order in the event editor. All objects that pertain to each other (eg: collision mask + sensors) are next to each other so i can quickly alter code for each individual object.
[MENTION=9754]Phi[/MENTION] - I used to use behaviors until I started running into weird scoping issues with them. Now with foreach loops built in there isn't really a need for behaviors. I might use them for simple things like applying effects such as fire to specific objects, but that's about it.