...but specifically:

1) Have a lot of hit/dam (obvious) and use a flail/axe if you're having issues against people that defend too well. If you're a magey AP, lightning bolt can do a lot at lower levels (MANGLES). Bloodlust helps a lot versus defensive heavy fighters (felar spear, assassins, etc). Crippling strike helps a lot to deal with them

2) Find targets you can just bash/trip to death and win easily, or summon/sleep/spell-up, or play dirty and catch people ranking.

3) Shock and awe - what scares people is lots of damage fast or being unable to move. If you can't sleep them, cause them to run....blind, fireball, energy drain, plague (big early village applicant killer), etc. If you're a decent chaser, you can kill most runners.

4) I'd say they get strong around 30. You've got enough mana to do most things in your repertoire, you usually have enough gear/skills/wands to survive a fight for awhile, and by then you should have practiced enough to be scary even naked (90 weapons, some perfected key spells, etc). But it's usually pointless to kill at 30 unless you're shooting for early edges....I like to only kill those that get in my way or interrupt learning until 36, so when you fight people for the first time it's new for them and a lot more intimidating.