Nails and Screws
Usually mouldings are nailed with millied wire nails. You can either let the nailhead end in height with the skirting board or countersink it with a nail driver. If you are going to use putty and then cover-paint it it's best to counter sink the nailhead. An old carpentry trick to reduce the formation of crackis when assembling mouldings, and without drilling ahead is to tap the the nail edge a little. Nails with a bulging, visible head is usually to be prefered. They exist in several different finishes. Phillips screws with countersunk head can also be used.
Drilling
Always pre-drill all hardwood mouldings and countersink the holes with a countersink drill. Pre-drill also pine boards if you have attach it near the end of it.
Mitre
It is important to have a good saw when doing mitre joints. For help there are mitre boxes with tracks for 90, 60 and 45 mitre's. A little more advanced aid is a manual mitre saw with a stationary saw and sturdy carriage in metal, which is then adjustable for various angles. In bigger projects it's a better idea to use a power mitre saw. When you mitre always try with short pieces first to see if you cut right. It isn't alway so easy to do it right the first time.
Practical típs about repainting
First wash the surface with an alkalic cleaning agent. Then lightly sandpaper it with sandpaper 240 - 320 grain. Repaint with a detergentbased or waterborne paint. Remember that if using a waterborne paint you will have to sandpapper it more carefully. Putty when necessary.