If your at a bar, club, mall, party etc... And you want to close on a girl you just met.

Wouldn't it be better to give your number to her and not get her's, so that you won't appear needy/instead more desirable and also make it easier to know if she is truly interested in you by receiving that 1 phone call. If you don't get that phone call then you know she really wasn't interested to begin with and so you can move on with your life towards the next one.

Or

Would it be better to get her number and not give yours?

Or

If you get her number then automatically give her yours?

Give your number it's a risk... It's very difficult that she will call you if you haven't created a good rapport.
I think it's better to ask her number phone, obviously not like 'hey give me your number, I'll call you soon!'.
You have to ask it whit an excuse. For example, if you are talking about the club, you can ask the number saying something like 'Hey, have you ever been at the X? It's pretty cool, we should go together!'.
You have to ask the phone number when you reach a hook point for not to appear too needy!

No. You're over thinking this. The best way to get her number is to make plans or invite her along to whatever you're doing on a certain day. Hand her your phone with the enter a new contact screen open while telling her to put her number into your phone. Then you call her phone so she has your number (also so you know that it isn't a fake) and have her put in your name or nickname for the name associated with that number. It cuts down on her being able to give you excuses when you call and takes the guess work out of flaking.

My personal rule is I'll try calling/taking her out twice. After that the number disappears if nothing comes of it. Sometimes it'll go into the party file to call her on the off chance she'll show for a party down the road, but she's no longer actually in my phone at that point.

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Hi, I'm A. Fahren and I'm an author. I love to travel, socialize, and am hopelessly addicted to movies. That's about it.

Generally speaking its better to have her number because women tend to flake when you give yours if you just met them. Unless your (perceived) value was very high at the time.

My number one rule is never to ask for a number.
For me, it's all about getting them so curious and interested inme that they ask for my number instead.

Now that that's said, I never expect all of them to call or text me - but the ones who are interested will.

It has worked out pretty well with a ratio of 60-70% of all the times I've given my number to those who asked.