Extend your battery life and turn off unneeded services ...
Spend a few minutes thinking about what you do and do not use frequently on your iPhone, and then turn those things off. Don't need Continuity and Handoff and don't use a Bluetooth headset? Turn off Bluetooth. Only very occasionally need to make your own Wi-Fi hotspot? Turn it on manually when you need it, leave it off the rest of the time (that one will save you remarkable amounts of battery life). Prefer to invoke Siri by double-clicking the home button? Turn off "Hey Siri" (if it is enabled).
Here's another couple of big ones that save a lot of power: turn off "Background App Refresh." Just turn it off. Everyone is different, so possibly you have an app (other than Maps, which will do so regardless) that absolutely has to refresh in the background, and in that case you can turn it on for that app, but turn it off for everything else. It's a little shocking how many apps "think" they need this. Does anyone really believe restaurant app Zomato will work better if it's allowed to continuously update its listings based on where you are at the moment, versus just opening the app, which causes a manual refresh? Apparently Zomato's developers do.
The second one is a bit more involved, because unlike background app refresh you can't really just turn it all off: Location Services. You’ll have to visit the Location Services pane (under "Privacy") in settings and manually adjust each app's settings. Most apps have three options: "Never," "Always," and "While Using the App." Some apps from good-guy developers have either "Never" or "While Using the App."
There are apps that need or at least have a good reason to make the case for "always" needing your location, like mapping and exercise apps that run in the background. That said, you’ll be dumbfounded at how many apps claim to "need" your location. Most apps that only offer "Always" or "Never" have been updated over time to use the vastly-smarter "While Using the App" option, but you'll find a few that want constant access. Broadly speaking, all apps that want your location to, for example, start your travel booking from the airport nearest you, should be set to "while using the app" if it makes sense to you that it would be useful. For all others, ask yourself if the app really needs to know where you are, chances are high the answer will be "never."
If you've done the above and you're still seeing more than normal drain, check the Battery portion of Settings. Here you’ll find a list of what's been draining your battery: just checking it now, I am not surprised to find that the big culprit in the last 24 hours for me was Camera. If I looked at that list and was surprised by the chief culprit(s), it might be time for a restart - a residual process or something might be going wrong. The Battery panel is also where you’ll find Low Power Mode.
There are loads of other, smaller things you can do to cut down battery use, but the whole pile of them won't add up to much unless you do every single one of them, and that's a lot more work. The suggestions above are largely "one time only" type things (with occasional revisits as you add more apps). One more that can also make a big difference: if you are out somewhere and you know there is no Wi-Fi around at all (like when camping), turn off Wi-Fi. Smartphones constantly look for Wi-Fi signal when it’s on.