Paper map
Compass
Binoculars or (usually) camera telephoto for spotting stiles in the next hedge
Assorted guidebooks - Cicerone, Wainwright, Poucher etc.
Bus & train timetable
For anything that looks iffy ---- river crossings in particular, internet searches, posting queries, pestering locals until I find someone who'll help me wade the Duddon or the Solway or whatever
This old-fashioned method has got me all round the perimeter of England (Coast + Offa's Dyke + Scottish border), up all the Wainwrights, about 100 Munros and all the 2000-ers in N Wales and the Brecons, not to mention along most of England's Long Distance Paths. So I'm inclined to stick with it. I did have an early GPS and found it useful when I was lost in mist above Kintail but it was otherwise a nuisance as I'd look, mesmerised, at it when I should have been watching where I was putting my feet. When it stopped working I didn't replace it. I have a 'robust' phone, resilient to being dropped, not a smartphone, and doubt GPS programmes would run on it, though I may be wrong.