Migrate from Sublime text 2 to Sublime text3

Your preferences/configuration from ST2 is in Packages/User (find it with Preferences -> Browse Packages). You can just copy that folder to to Packages folder in ST3.

About plugins it is best to check the already mentioned link: https://github.com/wbond/sublime_package_control/wiki/Sublime-Text-3-Compatible-Packages This wiki page explains which plugins can be installed via Package Control and which ones require manual installation.

Aditional info for windows users, to make ST3 as the default editor after migration.

If you keep both versions or if you uninstall ST2... probably you will notice that you can't open files or associate open with by default with ST3.

I think I can help you get Open With/default editor working.
The problem is that the Sublime Text uninstaller doesn't remove a particular registry entry referring to Sublime Text 2's sublime_text.exe, which prevents Windows from adding an entry for Sublime Text 3's sublime_text.exe.

To correct it manually, open regedit and navigate to:

Computer\HKEY_CLASSES_ROOT\Applications\

find the sublime_text.exe entry, and delete it. You should now be able to set Sublime Text 3 as the default editor for anything you want.

Source: Re: Can't make default editor in windows by @kane_t

I wrote a blog post detailing how to migrate over from Sublime Text 2 over to ST3.

Read: "Can I use ST3 yet? Migrating to Sublime Text 3"

TLDR:

1. Use git to install the python3 branch of Package Control. Step by step instructions available here;

2. Move over all your folders in Sublime Text 2/Packages/ to Sublime Text 3/Packages/ except two: Default and Package Control.