When I first starting looking at this the most common advice was check what you have already got under your home contents. In my case - with one of the high street providers the answer was not a lot so I did some research. In particular I was interested in cover for camera/optics stolen from an unattended car as most home policies are limited to £1000.
Best result I found was Home and Contents from Hiscox who offered better cover including "new for old", world wide as standard, no individual listing for items under £15k and upto to £2.5K for that unattended car. The online quote was quick and easy - and it came to less than my high street provider
So I switched.
I've only had to claim once for water damage from a broken pipe. It couldn't have been better handled. 1 Phone call for approval, no claim form required, sent them the workmans invoice and the money was in my bank 2 days later.
ps: I case you were wondering I don't work for them.