I am clearly a big fan of GMail and I have been for a very long time. With my clients I am always advocating switching to GMail and using the web interface as their primary email and productivity center. With a clean inbox you can accomplish some amazing things in terms of getting things done. Your email becomes your de facto to do list because anything in your inbox should either be deleted, deferred or dealt with. This is my step by step guide to making the switch as well as all of the tools and add ons you need to make GMail rocket you to the next level of personal and professional efficiency.
Make The Switch
Making the switch is really easier than you might think. Sign up for a free GMail account if you don't already have one. Then go to Settings, and then Accounts and Import. There you can import mail and contacts from a variety of email services. You can do this for multiple accounts so not only can you receive all your mail in one place but you can send from any account, all from one interface. The benefit of at least using GMail as your interface is that you can benefit from all of its productivity magic even if you don't completely abandon your other services. This also allows you to test the GMail interface with your current provider and if you get nervous or don't like it you can immediately go back to your Outlook Exchange or Yahoo account without any interruption in service. If you are hesitant about doing the migration yourself, check out MigrationWiz, which will take care of the whole process for you.
Once you've made the switch, go through the list below. I use all of these services in some capacity or another. Read the descriptions, add in what you want, and get closer to GMail nirvana with each step. This list will be updated every time I recommend a new service so you can always refer to this post for a complete list. If I missed anything that you like, please mention it in the comments.