My two cents, others will differ:
1) How many cities should I develop and how long after the first city should I start developing others?
a. There is no "number" of cities. Watch the slider and your main enemy is "STRIKE". My own practise is to halt at 30% because the dip from 30 to 0 tends to be too fast to counter when on a downward spiral. When you're back up to a surplus of gold at 30, consider more expansion. If you're at 40, 50, 60, and there's open land, GET it. One settler is easier than 600 axemen suicide-raiding Saladin's longbows, now isn't it? So get it now, if you can.
2) What are the first steps after setting up a first city? Do I build military first? Settlers? Workers? etc.
a. Unless you start with fishing on a coast, get a warrior going just so your city can grow to at least size 2 (preferably 3). The get a worker out, so he can work your food resource. When you've got your food going, your settler will build quicker. Use your warrior to escort the settler. If possible, keep the first city in a warrior/settler cycle until the second city has built enough units to where it can just do settlers full-time until all your cities are settled.
3) Is it best to automate workers or assigned them specific duties?
a. Assign them specific duties. Automation is the devil.
4) What is the best way to setup your military for defense? That includes within cities and outside of them?
a. On border cities, keep at least two City Garrison types (archers, and later longbows/crossbows), as well as at least one spear, one chariot, and 2 or more axemen. That won't stave off a HUGE stack, but it's enough of a deterrent that you won't lose it right away to a "recon in force" type of attack that some of the aggressive civs like to do early, with smaller stacks. In the "back" cities, cities not along a border or a coast, keep more of a skeleton crew. I typically keep it to an archer and a mounted unit, to bat away the odd barbarian incursion, etc. These units won't be built right away, but you should work toward that as a goal, of higher importance than building wonders and most building types except barracks, courthouses, and libraries.
If you have an "aggressive" civ next to you, increase the defenses to at least double the axemen, and have a mobile reaction force of axemen (and later, catapults) to respond to threats.
If you get attacked, all cities except one should switch to unit builds. The one that doesn't should be the top earner of beakers and coins (usually the capital), which should stay working on any buildings it needs, to increase its income, or, if those are built, to work on any wonders that might help militarily (e.g., Statue of Zeus) or with a technology boost (Oracle). Many other wonders will look enticing, but are not as important as they seem.
Good luck!