Condoms are most effective if you follow these steps:
Use a new condom each time you have sexual intercourse.
When opening the condom wrapper, be careful not to poke a hole in the condom with your fingernails, teeth, or other sharp objects.
Put the condom on as soon as your penis is hard (erect) and before any sexual contact with your partner.
Before putting it on, hold the tip of the condom and squeeze out the air to leave room for the semen after ejaculation.
If you aren't circumcised, pull down the loose skin from the head of the penis (foreskin) before putting on the condom.
While continuing to hold on to the tip of the condom, unroll it all the way down to the base of your penis.
If you are also using the condom as birth control, make sure your partner uses a spermicide according to the manufacturer's instructions. (Although the use of a spermicide increases the effectiveness of a condom as birth control, the use of a spermicide may increase the risk for transmitting HIV).
If you want to use a lubricant, never use petroleum jelly (such as Vaseline), grease, hand lotion, baby oil, or anything with oil in it (read the label). Oil (or petroleum) can weaken the condom, increasing the chance that it may break. Instead, use a personal lubricant such as Astroglide or K-Y Jelly.
After ejaculation, hold on to the condom at the base of your penis and withdraw from your partner while your penis is still erect. This will keep semen from spilling out of the condom.