Because I fly IFR where necessary, I carry a Jeppesen airways manual in the aircraft (it has a monthly update service).
However, the pages are very flimsy and easily damaged. They are also difficult to photocopy without print through from the reverse side for (I'm aware of possible copyright issues). So, if I intend to go to a large airport I often get the plates from the AIS website and print the plates in A4 size, especially the ground taxy charts.
Because I also go to small airfields and helipads I also carry the latest Pooley's VFR Flight guide. If you buy the loose leaf version, a quarterly update service is included, which I'd recommend.
I also PPR airfields, irrespective of whether it's mandatory or not, because of the nature of my job - if I need to go, it's important that I work in a highly professional way. This has proved to be a good idea on any number of occasions, when I was given essential new information that hadn't even been NOTAM'ed.