By tweeting this post, you can earn promotional tweets from me as part of the Amazon Tweet Exchange.
If you want to be taken seriously as an author, don't do the following...
Call Yourself a Best Seller
Calling yourself a best seller when you don't have solid proof hurts you more than not calling yourself a best seller when you actually are. If in doubt, just don't use the term at all. Chances are you aren't. And you look silly when you call yourself a best seller when most of us know you are the exact opposite.
When you definitely are not a best seller...
You aren't a best seller if you "gave" away said books.
Free days on Kindle, for instance
You aren't a best seller if you only hit a list for a few hours.
You aren't a best seller if you hit a sub-genre list in a less competitive market.
And even if you are a best seller, actually hitting Amazon's Top 100 site-wide chart, the overuse of the term from other authors could hurt you more. My personal recommendation: don't use it.
Spam People Directly on Twitter
I get these messages everyday. Someone will mention me in a promotional tweet about their book. Personally I don't mind. I can ignore you like any other unwanted tweet. Spam doesn't bother me, in other words.
But it does make you look bad, and others definitely will not take you seriously as an author.
I'm not saying don't put out promotional tweets at all. Unlike a lot of the advice you see out there, I think there is room for promotion on Twitter. People thank me for my tweets all the time, so I know it works. It may not be the best sales generator, but it is a wonderful way to expose.
Spread some seed and see what grows, but don't throw seed at people directly.