Banks need you more than you need them.
If you hold that truth in your mind, you'll have an easier time dealing with banks when negotiating with your interest rates.
Do you have good credit? Do you have a long history with this bank?
If you answered yes to one of the questions, you should be entitled for better service and that includes getting the best rate for your card.
Banks want your business especially if you're a loyal customer and how you take advantage of this truth can help determine a lower rate.
So, how do you negotiate your interest rate?
Step 1: Call the bank
Step 2: Tell them "how do I get my interest rate lowered?"
From this point, wait to hear your answer. If it's that simple, they should give it to you that instant, if not, move on to step 3.
Step 3: Ask "who determines if I can get my rate lowered?"
At this point, if they don't connect you with someone such as the manager, move on to step 4.
Step 4: Hang up and call again directly asking for the manager.
Step 5: Now, ask the manager the same question from step 2 and 3.
At this point, you should get a clear understanding what it will take to get a lowered rate. If they don't give you a lower rate after these steps, threaten to close the account (but don't).
The bank might give in and just give you the lower rate but from my personal experience the best way to get a good rate is actually to pay off your card in FULL... usually sooner or later they're going to offer you some 0% APR offer.