Two pairs of steps and a plank to start with to span the width of the room or the length depending on which way you are going.
Measure the length of the paper plus about two inches longer on each end.
Paste the paper with a good qaulity paste such as Solvite, slightly on the thicker side. Paste the paper and fold into a concertina shape with a small tail on it. Allow it to soak until pliable. Use a stick of a rolled up part of a roll of paper to act as a maul... to suport the paper whilst you hold it up.
mark the ceiling with a pencil line or chalk line allowing for it it lap onto the adjacent wall about 2". If you follow the line then the rest of the lengths will follows straight.
Get onto the plank and holding the maul with the paper over it open the tail of the concertina with your other hand and postion this on the ceiling and agaist the line. This is the tricky bit if your not used to it, whilst the paper is stuck to the ceiling use you papering brush to smooth out the paper whilst your other hand gently unfolds a section at a time of the concertina.
Once you have unfolded and brushed out the whole length then you can go back along it with the papering brush smoothing out any bubbles, out to the sides gently not too much preasure or you can stretch the pattern.
Run a pencil mark round the walls and trim the paper to allow about a half inch lapping onto the walls, this will then be covered bythe wall paper unless you are just painting the walls then trimm neat to the wall.
Can be a bit tricky to start with. Size the ceiling to allow the paper to slide a little so it doesnt grab. Good for you back bending backwards anyway...