Correct Pull-up form

I'm mainly concerned about the position of the back. Should I keep it neutral or should I arch my back a bit?

Also, I read that squeezing my glutes when going up will make the movement more challenging. What do you think?

I'll post a video in a few days.

Actually squeezing your glutes should make the movement easier. For some reason, if you tighten a muscle that is not used directly in a movement like a pull up, the muscles that are directly involved tense more forcefully, making you stronger in the movement. Even squeezing the bar tightly as if you were trying to crush it instead of simply holding on should amplify your strength. Something Pavel Tsatsouline nicknames "muscle software", though I can't think of the scientific name off-hand.

However squeezing your glutes may make pull-up more difficult by not allowing you to kip.

Gymnastics prefers a "hollow" pullup position rather than an arched back. There are gains to be had from having the back straight as evidenced in a recent T-nation article on Ab training.

Squeeze your butt, suck in your abs (squeeze them actually), then do the pullup.

You must master this straight body pullup position if you have hope to build to L pullups, wide arm L pullups, etc.

In gymnastics, quite often you'll see coaches have the girls tuck their knees and hold a pit cube or ball to flatten out their back.

Then again, our girls kip their PU or arch big time. Meh.

Yeah i think the term you're trying to remember is muscle irradiation, where the muscles contract and if other supporting muscles also contract it gives the main muscles in the exercise a greater boost and strength.