Trimming paper around and behind radiators
It is always best to remove radiators so that paper may be hung properly behind them.
If you are not happy doing this, it is perfectly possible to make a reasonably good job without removing them.
Switch off the radiator by turning off the valve or turning off the heating altogether. Allow it to cool - hot radiators tend to dry the paper out too quickly.
When you reach the radiator, hang the paper lightly over it, allowing it to drop down in front.
Measure the position of the radiator bracket in relation to the end of the radiator.
Mark the position of the top and bottom of the bracket on the paper.
Cut up from the bottom of the paper, through the bottom mark, to the top one. Then make a cut out between these marks to match the width of the bracket.
Now lift the paper away from the radiator and feed it behind, allowing it to hang down either side of the bracket.
Using a long-handled mini roller, smooth the paper behind the radiator before finally trimming in the usual way.
Trimming paper around fireplaces and other awkward shapes
These are actually not disimilar to window and door frames. They just have a lot more angles to deal with.
Hang the paper, lightly overlapping the item, then make cuts from the waste in towards each angle. Ease the paper back in to the profile, and mark and trim as usual.
If possible, try to mark the paper with the back edge of your scissors to provide a cutting line. Using a pencil can leave marks on the finished paper.