Spice up your account with an image, fill in your profile, get a good background. Make it welcoming for people so they can join. Note that I would say 90% of the time, human bot accounts follow you in an effort for them to follow you back, but the more followers you have of higher profile, the higher the chance that a higher profile member will follow you and so on, because of Twitter presence.
If you're advertising a website, make sure to include the link in your account. Also, it's best to have a name of some relevance to your niche, but that's optional. Then you want to be promoting your link with posts that interest people. Just having "Join this [link]" won't be appealing. Fergal has a Twitter competition at BAF with users needing to post "Make one post on Business Advice Forum & win $1,250
http://bit.ly/baf1250". Something like that captures people's attention. People like seeing "free" and "offer" as that can result in a two-way win.
Also, when you only have a few followers, it's best to stick to a tweet per hour or so, but not more. When you get more followers, people won't realize how many tweets you post, and there is a lower chance that your tweet will be seen due to more followers.
Also, greeting people when they follow is a nice way to start some conversation that could lead to them visiting your site. Twitter is all about the right words at the right time. Also, one great way to get people of your niche to see is to add the hash tag (#) in front of keywords. This gets listed amongst all the other hash tags, eg. Get #free #SEO advice: [link]. The "free" and "SEO" will be listed in a query page and so it will be seen by more of that niche as it's them who are searching for those tags.
Also, following others is a good idea, but from personal experience, if they have a much higher following to follower ratio, then they are really follower spamming in order to gain more followers. Good luck.