Generally, I do this:
1) update everything, run `rake rails:update`, and run the tests. Hope this works. If not, figure out if the error is mine or a gem's.
2) If it's a gem's, try to lock it to the exact version I was using and repeat 1).
3) If that doesn't work due to version issues, investigate if the gem has some sort of preview support for rails 4.
4) if not, either send a pull request or an issue.
Generally, I do this:
1) update everything, run `rake rails:update`, and run the tests. Hope this works. If not, figure out if the error is mine or a gem's.
2) If it's a gem's, try to lock it to the exact version I was using and repeat 1).
3) If that doesn't work due to version issues, investigate if the gem has some sort of preview support for rails 4.
4) if not, either send a pull request or an issue.