The form of birth control that has the least impact on your fertility after you stop using it is without a doubt condoms. Natural family planning or abstinence natural forms of birth control are also pretty favorable for people who want to get pregnant quickly. Men who don't have intercourse for long periods of time might have lowered sperm counts, but once you are back in the game that will likely resolve itself quickly. Pill users may need a little longer to conceive. Some prefer to use condoms for a while until their natural menstrual cycles return, so that they can be sure when they conceived and how far long the pregnancy is when they do get their happy news. This is not necessary, but a matter of choice.
Previous coil users can normally also get pregnant right away. In some cases, their cycles need time to return to normal as well. There is one big exception to the rule that women who were on temporary birth control can get pregnant very soon after stopping it, and that is depo Provera. There are reports that some women did not ovulate for as long as two years... after receiving their last injection! Take that into account before receiving a depo Provera injection, if possible. Finally, couples who have taken more radical measures are in a special boat. If you have had a tubal ligation, vasectomy, or adiana permanent contraception, the chances of getting pregnant are slim without intervention, and even following reversal. Adiana can't be undone at all.