Tips for starting out: you begin on the up stairs. Turn off training on all your skills. Go directly to the Orb and stand on it, and fight off the monsters that come for you until you reach experience level 2; then you can make oklob plants. If you can manage it without a monster getting to the Orb, step off of the Orb, and make an oklob plant directly on top of the Orb; then you and the oklob will spend a while defending the orb. Make traps and oklobs to help you defend the Orb until you are high enough level to begin making the different kinds of statues. Jellies are a big threat in the early game, since they won't be hurt enough by traps, there will be a lot of stuff on the ground for them to eat, and they're acid resistant (so oklob plants won't hurt them much); you may begin seeing jellies around the time you reach experience level 6, and as it turns out, the Zot ability you receive at experience level 6 is designed to help you fight jellies (among other things).
Allied monsters are currently not very pro-active about targetting hostile monsters when they are not within sight of you; they will target a hostile monster if they see it attack you, if they see you attack it, if you tell them to attack it, or if the hostile monsters attacks them (usually this happens if you make an oklob or statue directly in the way of monsters on the shortest path from stairs to Orb). In the next version of Zot Defense, I plan to improve monster AI so that your oklobs and statues and eels will more intelligently and aggressively target distant opponents; but until then, be aware that your friends will fight more effectively when you stay within sight of them.