Experience makes all the difference. Know your vehicle. Know your self. Know the terrain. Start small and then work your way up.
Getting part way up a hill and getting hung up or stuck and having to back down can often result in disaster, such as a roll over. So think before starting up, and have a plan as to what you will do if you must stop part way up.
And I will add in, know about those around you. Don't follow someone up too close behind them and hopefully the person behind you will give you some space.