You all probably know this, but I just found it out and it's been a great help for me when positioning the camera.
Select the camera view by pressing NUM PAD 0
Then, go to the view menu, top left, and select NAVIGATION, you can set the navigation type to WALK.
The camera then becomes like a first person view which you can move with the W A S D keys, to walk forwards and backwards, strafe left and right, and the Q and E keys take it up and down. You use your mouse to look around, just like in a first person shooting game. When you click with your left mouse button the mode is disabled and the camera position is set.
To save going to the view / navigation / walk every time, you can set a keyboard shortcut to in the preferences.
Go to EDIT, PREFERENCES,
Select NAVIGATION, and under Fly & Walk make sure WALK is selected.
Then, still in the preferences,
on the left select KEYMAP. (just under navigation)
At the top, make sure - NAME - is highlighted in blue.
In the search box type WALK
In 3D View - View Navigation (Walk/Fly)
Click in the box next to 'keyboard' and press a key combination of your choice. I picked Alt C.
Then click the 3 little lines, bottom left of the preferences window, and select Save Preferences.
I have Auto Save Preferences selected, which is a good idea for me!
Hope that's useful. It was for me.
Cheers all.
Martin.