How to get twitter followers without following back?

[nishi]

If you already have a website then it's best to highlight your Twitter handle in that website. Give people a reasons to follow you on Twitter by giving Twitter specific promotions etc.
Also you can try using some Twitter software to get followers. Since you're using it to promote a clothing line you can try targeting followers that talk about clothes. You can do that using software. If you're limited based on geographical location then you can use these software to target followers by location.
Additionally you can use a Twitter contest to get followers in a viral way. You can give one of your latest items as the price. More valuable it is the higher the chance of getting lots of followers.