There are so many different hymns in the hymn books(the Laudate has over 900 listed). Most churches have a repertoire of favourite hymns that suit the priest, congregation and musicians but sometimes these are not the most popular or well known.
Do you rely on the priest's suggestions only?
Or take advice from friends and family?
However, if you are a regular churchgoer, then choosing is less of a problem.
a) are not a regular churchgoer
b) go to a different church than where the service will be held
c) are not of the same religion as the deceased
d) don't like singing yourself and so have no idea what hymns are good or not
e) or just don't know where to start!
Your priest officiating at the funeral will have many suggestions to help, but often it's nice to go prepared with some ideas of hymns and tunes.
Here's some of our top 25 (actually 28) "hummable" funeral hymns, but more modern ones:
Can't remember how that hymn goes?
Here are some short audio samples of a verse and chorus of these hymns for funerals to help you decide what to use.