Well there are lots of variables FH!
As a minimum, wx and notams for Departure arrival and alternate airfields plus enroute notams will keep you legal. Of course, you don't know if the wx at your planned alternate is going to be ok until you have checked it. That is why we like a bundle of airfields to look at, so we can choose a different one if we have to.
Most people will have a quick check of some en route bolt holes too. Sig wx charts always feature high up my list of things to check too.
If there is weather like the UK has this morning then i would be looking at lots of airfields to get a view of the whole picture.
Most pilots (with some notable exceptions) will be happy to talk you through their thought process, at the time, if you ask them. If you get one of the "notable exceptions" just leave him be and be happy you only have to meet him on the turnaround!