So they've told you to go cut some steel. How do you decide how? Methods of steel cutting could include bandsaw, portaband, sawzall, deck saw, plasma cutter, or air arcing. Here's a quick rundown of your options.
Bandsaw
Cutting with a stationary bandsaw works well for repetitive cuts. You must use the right blade. Metal blades have smaller teeth and more teeth. Make sure everything is clamped into place first. And don't force the blade. Check with the blade manufacturer or the supplier who sold it to you, for blade and feed speeds. Cooling fluid must be used. Blade guards are necessary and you should be wearing leather or cut resistant gloves. A portaband will work for thin materials, but will take some time. Clamp the steel onto something sturdy. Use a sharp blade and make sure it doesn't get too hot.
Sawzall
The straight blade of a sawzall is handy when you want to quickly hack something up. They can also get in places you can't reach with a chop saw or angle grinder. The sawzall really isn't recommended for any matter of precision work, however. The blade tends to jump out of the cut and the longer the blade the more erratic the tip will be. Again, make sure you use the right blade.
Grinder
An angle grinder is versatile and inexpensive. For many hobbyists, it is a great way to get the job done. An angle grinder will cut through thin steel. The cut will be wide and there will be lots of sparks.
Plasma Cutter
Many have great success with a plasma cutter. It does take a measure of skill, however (you'll find plenty of articles here, just search). A cut with a gas shield will lend the prettiest results.
Air Arcing
Carbon air arcing cuts metal by melting it in the heat of a carbon arc. The open arc is independent of the gas jet. Air arcing is recommended when you're back gouging, preparing joints, or removing excess surface steel and defective weld material. The process is loud and creates lots of sparks. You'll need arc welding equipment, including copper electrodes. Don't forget the earplugs.
Torch Cutting
Before you begin, check your equipment. The fittings should be snug. Exact instructions will vary with gas type. Choose from propane, liquid hydro-carbon, and acetylene. Propane or MAP requires more preheating. LHC pressure depends on material thickness. It burns cleanly and without the noise of an air arc. Acetylene is common in many applications. Oxyacetylene is readily available.
You'll want to ensure that you are as comfortable as possible, even if working in some awkward space. Will you be able to move your cutting arm freely? Can you support it with your other arm or on a surface? Determine how far you can cut before you'll have to adjust something. Figure out where the scrap will fall. Make sure it won't be landing on your feet or someone else. If you can, clamp the drop to something so it will fall out of the way.
Make sure the torch tip matches the steel. Tip size is equivalent to how large the center oxygen hole is. The center hole forces air through the melted steel. This hole must be clean to get a clean cut. A track burner will allow the user to make very clean straight cuts. You can also use a guide. When you light the torch with a striker, you'll see that the acetylene flame is bright orange. Start with acetylene then add oxygen. The flame will go blue with white. When you hold the cutting trigger you can adjust the oxygen until the white blue flames around the center have clear pointy tips.
Preheat the cut. This will reduce moisture and temperature shock. Focus on where you will start the cut. When it is cherry red and melty, you're ready. Push the molten steel through the piece. Make the kerf smooth and even by moving the torch smoothly and evenly.
Whichever method you choose, please take the proper safety precautions. If you will be cutting with a blade, there may be flying pieces of debris. Eye protection is not negotiable. If you're going to be cutting with flame or an electric arc, tinted lenses are required. And always clamp down your workpiece when you're cutting with a blade.