I struggle with this too. I too never made that first move, and waited for them to make it. I also used to use liquid courage to help me get up my nerves. Here's what I've learned from trial and error. To make the first kiss, first decide if things have been going well. Have they been listening to you? Are they trying to make eye contact with you? There's small things that NTs do when they're interested. Girls will usually make small gestures like touch your arm or shoulder when they're talking to you. Mess with their hair, or clothes, giggling, leaning towards you. So, we've established that she's interested in you. Also, remind yourself of this fact, they are still there with you. This is a good sign that they're actually interested. If they keep saying about how tired they are, or how they have to wake up early for work/school the next morning, things may not be going well.
Here's the way to make the first move. Try holding their hand. See how they respond. Hand holding is very easy to do if you do it casually. If you're walking with them, walk closely to them and wait for your hand to bump into theirs and grab on. You can try using an excuse to holding their hand, such as taking their hand to lead them away from something. Or, if you're up to it, just grab it and hold on. They may break the hand holding after a while, but that's not necessarily a bad thing. If there's an excuse to it, then that's OK. If they complain about your sweaty palms, maybe you should reconsider. If you're sitting around somewhere, holding hands will work as well. I usually try to use an excuse, such as asking to see that ring they're wearing, I take their hand and look at it, ask them what significance it has, then just keep holding onto their hand while they tell me about it.
The way to make the move towards the first kiss is a little more complicated. Girls will do the usual grooming gestures, eye contact, etc... Also, look for them to play with their lips, licking them, or pinching them, or biting them. Wait for a break in the conversation, see if she maintains eye contact with you while you've both shut up for a moment. This is your chance, start to lean in and hopefully she'll lean in as well. Kiss her. If she pulls back, abort, and start over from the beginning. After the first kiss is well received, it's much easier from there on out because you know she wants to kiss you. Also, everything starts with a kiss, so from there on out, you're on your own.