Diagnostic Tree: Several Items Dead
What Has Caused Your Outage?
If you have reached this page without beginning at the Start of the diagnostic tree, you may do better to start there.
Several electrical items in your home are not working. You have a common troubleshooting problem and the one with the most possibilities. Let's try to narrow things down quickly. See if any of the following sounds like your situation.
Though you don't think a circuit breaker tripped, a recent heavy load (vacuum, hairdryer, rug shampooer, microwave, carpenter's saw) or a recent burning-out light bulb could do so. Or you may have forgotten a separate subpanel with breakers in the other end of the house behind a picture. Or you may not realize that many brands of breakers do not look to be in a Tripped position when they have in fact tripped. And you can't rely on the labeling in the panel to point you to the breaker that really has to do with your outage.
Consider also that an outage in homes built or remodeled since the mid-1970s can be due to the tripping of another safety device than a breaker: The ground-fault interrupter (GFI = GFCI). Is your outage limited mostly to outlets and mostly in either the bathrooms/garage/outdoor locations or in the kitchen/dining/nook area? If so, then it is very likely that a GFI receptacle in the same locations has tripped. We can suspect this even more if recently the weather has been wet, or you have had young guests who could have played with the GFI's "test" button, or you have had contractors using tools in or around the place. Few people know the location and number of GFIs in their home.
If little of this about breakers and GFIs corresponds to your problem and your life, you should probably proceed to grapple with the Open. But if you should look into the possibility that something is tripped off, continue reading here.
The surest way to see if one of the breakers has tripped (or has another problem) is to take the panel's cover off and Test for hotness at every breaker terminal. (If one is not hot, reset it in the way I will mention next). If you avoid doing this first test from a concern about safety or from laziness, a second-best procedure is to very firmly push the handle of every breaker in turn firmly to full "off", so that it perhaps even clicks in place, and then firmly click it to "on" (but don't be holding it on much, in case it wants to retrip for a short). A third-best attempt is simply to weakly press each breaker handle a little more toward on (or later toward off, but without turning it off) and notice if one breaker seemed to have more or less give or play to it than all the others; then do the firm off-then-on procedure just on it, remembering which one it is.
If any of this restored power, Learn why the breaker had tripped. If none of this restored power to your dead things, but when resetting you heard a definite hum or buzz or saw a flash of light there, you most likely have a short and the breaker has retripped; even without these symptoms a breaker that won't give hotness to its terminal, with the wire in it, but will show hotness there if you remove that wire and then turn it on, is tripping for a short, so go to Short. If the wireless breaker shows no hotness when reset, it needs to be replaced and possibly in a different location in the panel.
If the breakers are now good and not tripping but your outage remains, Consider if a tripped GFI is the reason before concluding it is an open. Finding the one GFI that may be responsible for the outage can be hard. [A quick near-confirmation that a GFI somewhere is indeed tripped would be to test the continuity between neutral and ground holes at one of your (completely) dead outlets; continuity would tend to mean no GFI is tripped, while little continuity would make a tripped GFI likely]. Is it behind shelves or boxes in the garage? Is it in a rarely used powder room? Is it a rarely used outlet in a bathroom? Is it behind a dining room china hutch or tucked back in an "appliance garage" cabinet in a corner of the kitchen? By 1996 all new accessible receptacles outdoors, at wet bars, in bathrooms, garage, kitchen, dining, nook, pantry, crawl space, and in unfinished basements were to be GFI-protected; so the GFI devices themselves tend to be in these places. In regard to the kitchen/dining area, I would look for two, not just one.
If you do find one whose reset button is popped out, push it firmly in once or twice. If it resets and restores power, you are done (why it tripped may remain a mystery). If it pops back out go to Ground-fault. If it holds in but your outage continues, I suppose you could look for another tripped GFI somewhere. But it's starting to look like, by a process of elimination, you should go to Open.