SuperTip #1 - Don't make too many levels
It may seem like a basic thing to say, but many amateurs will get in and create levels for everything little thing, which results in a huge mess as the project progresses. Try to make the minimum amount of levels possible. These should always coincide with the major structural floor levels of your building. An excess amount of levels will make the project difficult to work on and difficult to work in. Please refer to this previous post for some tips on how to deal with this issue.
If you create heaps of levels, it will be very difficult to track which level elements are created on. For assistance with this, please refer to this previous post.
Instead of creating unnecessary levels, consider using reference planes in areas where you would normally put a superfluous level.