Talking about rules of thumb, i know a few programmers and most of them are so bad at it, maybe a few rules of thumb could help people who have bad programming practise.
Always comment your code well so you can return to your code anytime and still understand it fully
Always use descriptive names for controls and variables, also use naming conventions so you can know the type of control or variable.
You can use regions in your .NET IDE to separate code. E.g. I do it like this. (see Figure 1.0)
VB Code:
#Region "Public Declaration"
#End Region
#Region "Form Code"
#End Region
#Region "Sub Procedures"
#End Region
Your regions can then be expanding or contracted so that you can only see the code for regions you have expanded, this helps me focus only on the code i want to.