How to haggle

Going to be looking at some cars in a few days
first time buying a car. Read the sticky, but what are some tricks to haggle.
having cash on hand is a good idea I've heard, also dont compliment the car and stay neutral

Point out every minor flaw and after test driving say "it's nice, although I do have another [insert car here] lined up for [5-15% less than the car's value]"

That was actually the next thing I was going to ask
I'll be looking at 3 cars in the same general area
and I guess you already answered the question if I should mention that im looking at more cars after this one

Research how much the car is really worth. Try to find out how much the dealer paid for it.

Make the dealers compete with each other for your purchase.

Don't finance it through the dealer.

Most important: Don't be afraid to walk away. If Dealer 1 says $20,000 tell Dealer 2 they have to beat $20,000. If they say no, walk out. If you're in this haggle for the long haul, give them your card and they can call when they've changed their minds

not going to dealers but I assume it still applies
not going anywhere near 20k though

Not op, but whats a good price guide to trust?
KBB almost always undervalues stuff like 80s and 90s sports cars and NADA will always overvalue stuff. Edmunds also overvalues too i think

Ask for extras as well,

have a realistic price you won't go over

be ready to walk the fuck away...which will usually result in them agreeing with your price

How do you figure out what the dealer paid for it?

What about checking the general condition of the car, like repairs and maintenance history and the like? I've never done much car work beyond basic shit like oil changes, so I feel like I'll end up letting a lot of small details slip.
I want to try to nitpick but I don't think I have the eyes for it with cars just yet. Are there any easy finds that would notably affect the value?

what cars? budget?