well in depends on what baits your talkin about ?
16,14,12,few maggot,corn,pellets,meat,cheese ect,
10,8,small boilies(8,10,12m),bigger meat,cheese ect, 6,4, bigger boilies (14,20m)
i also would say use animal hooks they never let you down !!!
Happy fishing !!!
Again all depends on what bait your using or fish your after!
single maggot on a 20 double 18
Then worms again depends on what size your bait is a 6 inch lobworm wont catch anything on a size 20 hook let alone stay on it so put one like an 8/10 even down to a 4 on just something to suit the bait size. I know a bloke who uses a size 2 with two huge Lobworms and catches 6 oz chub on it.
Luncheon Meat can be cut acording to what size hook you are using but corn usually is a 14 or 12 for a couple of grains!
Also have to agree with Stiffler Animal hooks barbed and barbless all brilliant 
Now bolies i dont have a clue as never used them