Katas should be practiced with the following in mind:

Ensure that each stance is the best you can make it.
Imagine that attacks are real and execute your techniques accordingly.
Try to relax until the final moment of the technique
Relax after the technique
Aim to use the correct timing and combinations.
Don't forget to breath.

Practice, practice and then practice some more (you can even practice Kata in your head. Try It!!!)

If you are not sure of something don't be afraid to ask a Sensei or Sempai for help

Pinan Katas

Pinan Nidan,  Pinan Shodan,  Pinan Sandan,  Pinan Yondan,  Pinan Godan

Brown - Black Belt Katas

Kushanku,  Naihanchi,  Seishan

Dan Grade Katas

Bassai,  Wanshu,  Rohai,  Niseishi,  Jitte,  Jion