A problem a lot of people suffer from is lag. The most simple of models can be ruined by bad framerates and there is a simple way of fixing this.
Groups
Although they can reduce the files size groups and components inside the main body of a model, so the first thing to do is make sure there is as few fgroups inside your main body as possible. for instace, if you're making a car, don't put the doors, mirrors etc as different groups if they're going to stick on the vehicle
View settings
Another thing that holds down a model's potential is the view settings. turn off shadows, edges, profiles and textures to further reduce lag on an sp model.