For example, Evolving Wilds has a mana fixing ability, but it doesn't say you can tap it for mana. Other non-basic lands have a mana ability listed on the card. Should I assume that Evolving Winds cannot be tapped for mana?
Basic lands don't have mana tapping abilities listed, but are assumed you can tap them for mana of the color they represent.
No, you cannot tap non-basics for mana unless they have an ability that specifically says otherwise.
Basic lands are handled with a special case in the rules:
305.6 The basic land types are Plains, Island, Swamp, Mountain, and Forest. If an object uses the words “basic land type,” it’s referring to one of these subtypes. A land with a basic land type has an intrinsic ability to produce colored mana. (See rule 406, “Mana Abilities.”) The land is treated as if its text box included, “Tap.gif: Add [mana symbol] to your mana pool,” even if the text box doesn’t actually contain text or the card has no text box. For Plains, [mana symbol] is {W}; for Islands, {U}; for Swamps, {B}, for Mountains, {R}, and for Forests, {G}. See rule 107.4a. Also see rule 605, "Mana Abilities."
