Here are some of the techniques I use when making and decorating a cake.
The baking tin is lined with baking parchment which, especially with the chocolate sponge cake, needs to be removed while the cake is still warm (not hot straight from the oven, though). I have found that the parchment tends to stick if the cake is cold - or very hot - and then on removal it also takes away some of the cake!
I use apricot jam (seived to remove fruit lumps) to stick almond icing and fondant icing onto fruit cakes, and butter icing (using hard stork) of the appropriate flavour, to fill sponge cakes and to stick on the fondant icing.
For the piped decoration, I use packet royal icing, with a small quantity of glycerin added to prevent it going rock hard (not too much glycerin otherwise the icing tends to be powdery and difficult to pipe). I also use fondant icing and modelling icing to make added features. In the past I used jelly colouring for the icing, but now I find the powder colours much more versatile.
It is very helpful to have the cake on a turntable when decorating with piped icing as it is so easy to damage the decorations on the side when turning a cake without one.
One thing I always found annoying was that using an icing bag was very messy - the icing tends to be squeezed through the bag and cover my hands. However, I found some plastic icing bags at our local suppliers of sugarcraft equipment ("Items" of Kenley) which cut the mess down considerably. They could not be used alone as they stretched and would not hold the piping nozzle; however, used inside a cloth bag they do a very good job of keeping hands clean.