I've been to Blackpool twice now and the only real reason I visit there is to spend time with my friends and to go on the rollercoasters at the Blackpool Pleasure Beach.
The Pleasure Beach is well worth a visit especially due to the rollercoasters such as the Pepsi Max Big one, Bling, Spin Doctor, and to scare yourself silly in the Pasaje Del Terror.
There are many other rides and attractions and details of these can all be found at http://www.blackpoolpleasurebeach.com.
The Blackpool Tower is also worth a visit. For £12.95 we got entry to the tower and all attractions inside. It's fun to stand on the glass floor of the tower and even more fun watching people who are afraid of heights cower as someone pushes them onto it. They also had a circus which featured a number of acrobats from Russia, Hungary and China. They were very skillful and well worth watching.
Quick Tips:
If you go in the Pleasure Park, it is best value to buy the wristbands. These let you go on the majority of rides within the park as many times as you like and works out considerably cheaper than buying single ride tickets. The wristbands also let you get a free meal in some of the theme park restaurants (see details when you purchase).
Best Way To Get Around:
There are trams which run all along the sea front and to the main attractions. There are hundreds of taxis which are a reasonable price as well.