1) Are any fish rising/moving in the margins
2) What fly life is on or coming of the water
3) Is the water Clear/Opaque/coloured/Muddy?
This will determine how or whether you start to fish
If river fishing the above applies, but also beware of high banks, they could be undercut! ie you could be standing/kneeling on nothing more than scrub/grass.
Before fishing into the next pool its sometimes better to wait a moment, fish hold at the very tail of a pool.
ALWAYS wear eye protection, and some form of headwear.
ALWAYS take care if fishing near overhead power lines
Finally, BEWARE of people passing behind you.You will only hear someone behind you, when you catch them with your hook.