Start by going through your bills very carefully to see what has changed. It might be a rate change, e.g. summer/winter. The basic unit of billing is a kilowatt-hour (kWh), and is typically 12 cents a kWh in most of the country. Also, some utility web sites will let you see hour by hour usage, typically finer resolution than that.
A typical toaster takes 1000 watts or 1 kilowatt (kW), so using a toaster for an hour is a kilowatt-hour. Also a lot of toast lol.
Most heat appliances (coffeemaker, heater-fan, griddle) take 1500 watts or 1.5 kilowatts. One of those for 40 minutes is a kilowatt-hour.
Now, get conscious of what your loads are.
How do I know what appliances take? They have a nameplate that tells you. Sometimes you see watts stated as a different unit called VA (treat it as the same)... other times it's listed as amps (A) and you must multiply by whatever its voltage is to get watts. So if you have a 22 amp water heater, well those are 240V so 240x22 = the watts (a lot).
For some appliances, nameplate is only "maximum" and they often take much less. For loads that plug in, you can use a gadget like
@dmxtothemax showed you - Kill-a-Watt being a common brand sold at Walmart.
For hardwired loads (air conditioner, water heater etc.) they take their nameplate but only when they are cycled "on".
Learn to watch "real time/live" action on your electric meter.
The 5 digit number changes very slowly and is not worth watching.
The old electric meters with the spinning discs, you could just watch the speed of the disc. There's even a formula for how long it takes to make a circle. Today, smart meters have *some way or another* of watching the "wheel spin". And you can get the model number off your meter and google the instructions and read them. Some have 3 little lights that do sort of a marquee chase, so you can see speed of usage (and time it with a stopwatch if you need hard numbers). Others, you push a button to get to a screen that shows you instantaneous usage.
Now, watch for high usage. If you see it on the meter, start turning things off until it goes away.