Using 有点儿 before an adjective indicates how you feel, especially about something you are not satisfied. For instance, 这件衣服有点儿贵, or 我最近有点儿忙. Using 一点儿 after an adjective is usually to compare things/situations and make your requirements. For instance, 这件衣服有点儿贵，便宜一点儿可以吗？他再开心一点儿就更好了。

--Echo

echo@popupchinese.com