Is there a way to see how close we are to leveling up?
When you reach lvl 15, you can travel to china and pay 75000 to see the precentage of your current level before leveling up.
Also, is there any tricks or tips for leveling up quicker?
Attack people higher level than you and clicking the leave option, the guy above also have a link to a guide that help
Why is there an option to hold off leveling up? Is there a reason we should be holding?
Most people level hold to make others think they are an easy target, and getting the defends. Level holding also make it easier for people to bust you out of jail.
Downside of level holding: lower life (5th stat), and it's harder for you to bust people from jail.