You need to figure what types of lights you have to do the design and what types of light those lighting instruments give off. Smaller theaters will have a combination of ellipsoidals, Fresnel, and par 64. Ellipsoidals are the "longer" looking lights and provide a sharp directional beam. Fresnel are the more square lights and they can go between a spot or area lighting; they provide a good area of light. Par 64's are a bit longer than a Fresnel and are great for area lighting. Depending on how many lights you have, try to use the same type for the same use. For example, if you just want to fill the stage with an even light, don't combine Fresnel and ellipsoidals as they will give different qualities of light and your wash will look uneven.
You will need to separate the space into areas. You should always separate into multiples of three and how many multiples will depend on how big the space is. The three areas will be stage left and right and center stage. If your stage is deep enough, begin to add rows of areas. For example, a six-row area would consist of downstage left and right, upstage left and right and down and upstage center.
Ideally, each area will have three lights pointed at it. Using gels, you will need to add some color to these instruments. From one side, the area will have a "warm" light pointing at it (using an amber gel). From the other side, the area should be lit by a "cool" color (such as a very light blue). Finally, from the center, there should be a neutral, no-color "fill" light. These three lights will make the actors look three-dimensional on stage. Light from the front is called front light and an ellipsoidal or Fresnel is good for this. If you have enough instruments, think about adding "top light" (light that comes from above) to round out each area. This is best done with a Fresnel or ellipsoidal.
Once you have your lights up, gelled and focused, you will have to patch them into the light board. Lights are plugged into circuits. Those circuits are "patched" into dimmers. The dimmers are then assigned to light board channels. The easiest way to patch your lights is to place each circuit (i.e. each place where the lights are plugged into) into its own dimmer and each dimmer into its own channel. This will keep everything easy as you go to turn the lights on and allow you flexibility in setting how bright the lights are. Try to keep all of your warms, cools and fill lights together. (If you have three areas, channels 1 to 3 could be warm, 4 to 6 could be cool and 7 to 9 could be fill). If you don't have that capability, organize your dimmers and channels in such a way to give you flexibility. An easy thing to do when this happens is to keep your "area" together so you can at least isolate different places on stage.