What is your application versioning strategy? [duplicate]

Question

This question already has an answer here:

• What “version naming convention” do you use? [closed] 13 answers

I would be interested to get the SO community's opinions on the best application versioning strategy.

My questions:

1. How do you keep track of your application's version number? Do you have a formal definition of what each number/character in that version represents?

2. What do the different numbers/strings in the application's version mean for your app?

3. Do you use any automated updating system in your apps (e.g. something like Sparkle) and how good has it been behaving for you?

4. Do you have a separate update procedure for beta-testers or pre-release testers of your app?