I've heard that on it's own the pill is around 99% (maybe even 99.9 I've heard). However other people have told me it's around 97%, so I'm not entirely sure. It's definately in the high 90s though, it is VERY reliable, pregnancies resulting from the Pill failing are rare if you take it correctly.
I don't know an awful lot about the Pill, I'd like to know the same thing regarding the MiniPill.

The birth control pill, when used CORRECTLY, is more than 99% effective when preventing pregnancy.

However, most people do not use their pill correctly, so new data figures have been recorded for those people who experience "typical" use. These people sometimes forget pills, take them late ( 12 hours for the combined pill and 3 hours for the MiniPill), take contradicting medications (such as St. John's Wort, SOME antibiotics like Rifampin), or experience diarrhea and vomiting which can decrease the pill's efficacy. For these people, the pill is around 92%-97% effective.

It is pretty hard to get pregnant on the pill, even when your a typical user. The pill prevents ovulation, which must occur for pregnancy to occur. It also thickens the cervical mucus, which makes it very hard for the rare case of a fertilized egg to attach to the uterus.

If you want to be in that 99% efficacy region, just take your pill around the same time EVERY DAY. Setting an alarm clock is a good way to remember. Also, carrying your pills with you at all times is another good way to make sure you never forget a pill.

Also, know what to do in the case of a missed or forgotten pill. This information, and other valuable information like it, can be found in your pill booklet (which is usually also online). In this case, it's good to read the fine print and be prepared.

I'm just curious, where did you get these figures and are you a professional?

http://www.fda.gov/Fdac/features/1997/conc eptbl.html

the FDA released a chart graphing their collected data regarding birth control methods. I have seen varying statistics for "typical" use, however, "perfect" use always puts the pill at more than 99% effective.

I am not a professional but I know a good amount about birth control from my own experiences. Also, I do a LOT of research when I'm worried about something, and I tend to find the most credible sources before I believe anything. Therefor I decided I would like to be able to share accurate information, since "googling" your symptoms or concerns always ends in inaccurate information and more worry. If you'd like, I can find good sources for any of my information above, or any other information I can provide you.