This is perhaps not a tip as such, except that reading MSDN magazine is something every .Net developer should do regularly - so my tip would be to read each edition.
There are many, many useful MSDN articles and I just want to provide links to some that provide very useful information for those of us that work with that platform.
Digging into IDisposable[^] by Shawn Farkas - October 2005
It's worth noting that sometimes
void Dispose(bool disposing) is incorrectly implemented like this:
protected virtual void Dispose(bool disposing)
Obviously this turns
Dispose into a mandatory operation. The information about security and garbage collection is also well worth noting. So basically you should never rely on the garbage collector cleaning up native resources correctly and always make sure you call
Writing Reliable .NET Code[^] by Alessandro Catorcini and Brian Grunkemeyer and Brian Grunkemeyer - December 2007
The article provides insights that are useful when you have to write reliable applications, and it explains why your web application may be terminated at any time – something that seems to surprise a lot of people.