Before you paint your walls I presume you would be giving the ceiling a coat of paint too, bring the ceiling emulsion onto the wall a couple of inches, then when you come to cuttin in the wall paint will flow easier along the ceiling line of the wall.
Dont have your paint too thick either, as can cause a dragging effect.
Do your cuttin in top, sides and bottom on one wall at a time, then roll, then go to the next wall, for the DIYer this will be a better way for them.
For the skirtings, mask up the carpet with wide masking tape, and place protective covering on the carpet.
When you come to painting your skirting, and you are cutting in on the bottom of the skirting (where the masking tape is) dont load your brush, just go lightly, cause if you do it too heavy, the paint can seep into the masking tape, and when you remove it, you can get an ridge, dip your brush into your pot, remove the excess, then go along the flat of the skirting a few inches, that will take the majority of the paint from the brush, then before your due to dip in again, just curve the brush at the bottom gently along the masking tape, and you wont get any bleeding into the masking tape.