Do not worry about being "green as grass", we were all green at one time. I am glad you mentioned your DMM. A few things about them. This are some things a "newbie" should know as well as a refresher for the experienced. Complacency kills elctricians. Seasoned electricians usually get hurt from rookie mistakes.
Meters in general will only tell you only what they are “seeing” at the probe tips providing the meter is not broken. They will tell you nothing more. It is up to the operator to determine what the meter is saying or not saying. The more you know about electrical theory, the more confident you will be using them.
A common problem with DMM's is measuring voltage. At times, you will register a voltage and it can be the voltage that is suppose to be there, yet the circuit will not work like it should. You may get odd voltages that should not be there. A couple of reasons for this is you are measuring is backfed voltages and what some call, “ghost” or “phantom” voltage. The link is a posting a while back that discuss this in more detail. When in doubt or troubleshooting, use the Wiggy first. It has a solenoid that puts a load on the circuit and that is the voltage you usually want.
https://www.electrical-contractor.net/forums/ubbthreads.php/ubb/showflat/Number/66737/page/0/fpart/1If you will be doing troubleshooting or working with equipment that have tight voltage tolerances, get a good DDM that is RMS rated (Root Mean Square) for voltage and amps if applicable. They are little pricier however when you are working on something with electronics, a ballast or transformer, the voltage reading can be way off. I have heard as much as 50%. You will be just running around in circles.
Learn how to use the meter properly. Some models like one with auto ranging take a couple of seconds to register a reading. In a rush and if you quickly take a reading, you may miss something which can be the biggest mistake in your life. Misuse of a meter can cause it to literally to blow up in your hand not to mention it can short out what you are metering. My meter for example will beep when it gets to the right range. It it does not beep, It is not done measuring.
Since you are just starting out I would not worry about these now. It is just food for thought. Good co-workers will watch out for you. I would suggest in the mean time and if the sparkies you are working with are willing to let you use their meters, try out the different models and ask questions. Ask them what they like bout them and what not. All of them have their pluses and minuses. Some sparkies are very protective of their meters and for good reason. They pay good money for them and their live literally depends on them. I would get a good working relationship with them before asking them to use their meter. You want a meter you feel comfortable and confident with that fits your needs. Your life depends on it. Using a meter that you are not comfortable with can make for an uneasy work day.
When metering think before you do.
