All you are trying to do is close up the case mouth where it was expanded to allow seating of the bullet.
You don't want to get the crimp so tight that it mars the bullet. Pull one and make sure the bullet isn't dented. This is particularly important for plated bullets where the plating may be damaged.
I check my rounds by putting a pair of dial calipers along the length of the cartridge. I don't want to see air behind the case mouth because the case mouth is too high and I don't want to see the case mouth rolling into the bullet.
There's one other concern besides the bullet fitting the chamber. If the crimp isn't tight enough and the case mouth is too high, the cartridge at the top of the magazine can 'trip' the case being ejected and yank it off the extractor. This problem is even more apparent when loading semi-wadcutters or any bullet with a ledge close to the case mouth.
Just close up the case mouth; not too much and not too little. Just closed...
"No matter how cynical you become, it's never enough to keep up." - Lily Tomlin