Guppies are happy with standard sort of temperatures-24 C or so. Since they are quite active little creatures it helps to have a tank big enough- I'd say at least 10 gallons. They appreciate things to interact with- plants, ornaments to swim in and out of. Male guppies prefer not having a very strong current as they are not brilliant swimmers.
They will really benefit from a varied diet- alternate ordinary flakes with spirulina flakes and/or vegetables (cooked peas, broad beans, sprouts, broccoli whatever) and the occasional treat of livefood, like bloodworms or daphnia (frozen or jellied is fine, doesn't actually have to be live).
You can keep either all females in any numbers (which I like, as they are stronger and less sex-fixated) or all males (at least 5 of them to spread aggression) or mixed genders, in which latter case a ratio of 2-3 females per male is best. Expect fry if you leep any females at all, and remember that if they have once mated, whether in your tank or the shop, they can make the sperm do for an awful long time...