Two ways of looking at this. My prefered option is not to even go there – camping kit and techy singletrack just don't mix! However if you are determined to do so then the two options are:
1) pack everything on the bike. Keeps the centre of gravity lower and wastes less energy – but you can no longer move the bike around under you nor lift the rear wheel so requires you to ride in a smooth style using momenteum.
2) put heavy stuff on your back – this takes more energy as you end up moving the weight of the rucksac around and might well give you backache – but you can still throw the bike around and kick the rear wheel up over steps. Your centre of gravity will be higher and this can make falls more spectacular.
I use option 1 but I tend to ride longish days of 40+ miles and when the going gets tricky just push the bike.
for shorter but techy days out use option 2