How to ask for Donations?

The blogs that are carrying or dedicated to personal development or productivity topics may add a ‘donation’ button. It may work well, there are many blog doing well like Steve Pavlina.
Off late a small variation of this has come with WordPres plugin ‘Buy Me a Beer’. This variation is also doing well with some blogs , a massage comes at the bottom of every article and readers, if wishes, can chip in bucks for a beer or coffee.