Again...Maps is one of the most useful applications, including the sat-nav feature.3/ Maps - Try not to use it. If you do it seems to start up a background process that continually monitors where you are so that next time you use Maps it is ready and doesn't need to search. If you must use it, afterwards go into 'Manage applications' and clear all data for Maps which will get rid of it. Force stop won't work - it will respawn.
Incredibly useful when using Maps...5/ Settings->Location turn off WiFi and GPS. Again, you don't need to know where you are that accurately and neither does anyone else. Turn them on if/when you really need them but by default leave them off.
What I do do is put the wi-fi and data toggles on the front screen, and they often get turned off manually on camp, or if battery is getting really low put it in flight mode and check voicemail once an hour just in case. But in normal usage I'd rather charge daily, just plug it in by my bed (as I use the alarm to wake me up). If nothing else it prevents me forgetting to charge it.
That said, I did add a double-capacity battery pack. With the normal battery and my normal usage on an original HTC Desire, I wasn't even getting a day out of it. The battery pack makes it bigger but easier to hold, so no real disadvantage.
 I haven't worn a watch for years, so with it off completely it leaves me not knowing the time.