I've been working around electronics since 1988, earlier if you count taking apart electronic equipment as a kid. Most of the time it worked when I put it back together, but not always. I have taken some pretty good shocks over the years and am writing this so that maybe you can avoid them. Most current inside electronic equipment is DC, or direct current, but household current is AC, or alternating current. Amperage, also known as current, is what is dangerous, not voltage although high voltages can make miniscule current dangerous as well, so it's best to just avoid it completely. I have heard that DC will grab onto you and make it hard to let go while AC pushes you away, but have not tested that theory to any conclusive finding and prefer to keep it that way. The following list of safety rules is not all inclusive and is provided as a reference only, but it should keep you alive.
1. Always make sure the power is disconnected when working on equipment.
2. Capacitors keep their charge for a while after power is removed. You can discharge them by holding the power button down for a few seconds usually.
3. Before touching anything inside of equipment, ground yourself by touching the bare metal case and prevent static discharge by wearing a grounding strap. Carpet makes static electricity so make sure to remove it from work areas.
4. Use insulated tools when working on power supplies or anything that has high voltages. Power supplies and power boards inside TVs have parts which can exceed 10,000 V.
5. If you take a power board out of a TV, do not put your hand on the back side of it, it will not feel good and may kill you under the right circumstances.
6. If you run into a CRT monitor or TV, be very careful when working around the tube. It can carry voltages in excess of 30,000 V.
7. Keep your work area clean, well lit, and well ventilated.
8. Be careful when soldering. Some solder uses lead and the fumes can kill you.
9. Soldering irons are hot. Do not touch anything in front of the handle. Make sure to use the proper stand to hold the soldering iron.
10. Always use the proper protective equipment (PPE) such as proper gloves for what you are doing, safety goggles or glasses, closed toed shoes, or anything else needed to safely work on the equipment.
11. Always be aware of what you are wearing. Rings or bracelets need to be removed, necklaces need be tucked in, and watches should be removed unless they are rubber. Any sleeves or other parts of clothing should be kept away from equipment.
12. Hair or beards should be tied back so as not to get caught in equipment.
13. When working with lasers, make sure to wear laser glasses so the light doesn't damage your eyes. Some lasers are invisible so it can do damage even if you don't see it.
14. Various chemicals can be used when working on electronics. They can have dangerous fumes, be toxic when ingested, or when touched. Make sure to read all caution labels and warnings. Keep a kit handy for cleaning up spills.
15. Make sure to have a fire extinguisher and first aid kit readily available. Eye wash stations are nice to have. Safety showers are also nice, but overkill for most applications.