Here are some tips I can think of, which I have learnt from making mistakes:
1. Make sure all old nails and clouts are removed from the studs and nogs before fititng new linings. Failure to do so will result in a hole being punched through the new Gib. Be especially careful not to miss the finer nails that held the scotia, architraves and skirting in place.
2. If your walls measure 2450mm (for example) from ceiling to floor, do not try to cut costs by using a 2400mm sheet. The gap left at the bottom (it will have to be the bottom, as standard scotia won't cover than size gap at the top) will mean that when you refit the skirting it will pull in at the bottom, looking all wrong.
3. When fitting Gib to the framing timber, do not glue it. Use 32mm gib-grabber screws. DO NOT over fasten and "pop" the paper on the Gib board. If you pop the paper the Gib WILL move, and you will be left with little circular indents which the painting will highlight. If you pop the paper, remove the screw and re-fix 5cm below (or to the side if fixing to a nog).
4. Make sure you plan out how the Gib is going to go on the wall. At some point you will need to join two straight edges together (as opposed to the beveled edges that the sheets come with). You get a straight edge when you have to cut a sheet to less that its factory width of 1200mm. If you are forced to do this in the middle of a wall, then you will not be able to tape the join. The result will be a hairline crack in the plaster, which will bug you for the rest of the time you are in the house. Try to get this inevitable join in the least noticeable internal corner of the room (e.g., behind high kitchen cabinets.
5. Tape all joints before stopping. For internal and external corners, use Gib Goldline Platinum strips. (I have found the easiest way to keep the Goldline in place is to use Ados F2 spray adhesive.) For stopping, use a jointing compound like Plus-4. This won't sag like a sloppier compound. Under filling the first two coats is better than overfilling, as less sanding will be required (and thus less mess). Stopping walls is easier than ceilings!
Getting the right tools for stopping (such as 150mm, 20mm and 280mm trowels, internal and external corner trowels) is not cheap. If you won't be doing this kind of thing again, it may well be best to get a professional in to do the job. You don't want to spend the next few years in a house looking at all of the little mistakes you made.
6. For good fits around light switches, remove the switch and use a terminal strip to cap the wires. Make the hole in the Gib only as big as the wall box the light switch panel screws into.
7. Try your best to avoid joining sheets above a door - it is hard to avoid cracking around doors due to the movement.
8. Where there are unavoidable small gaps where the scotias, architraves or skirtings meet the Gib, fill these with Selleys No More Gaps. IMMEDIATELY wipe off excess filler, as this stuff sets quite rubbery, and is difficult to sand. Do not use a non-flexible filler to fill these gaps.
9. Do not use the household vacuum cleaner to vacuum up dust produced by sanding the stopping compound. This WILL kill a household vacuum cleaner. If you don't believe me, ask my wife what happened to our previous two vacuum cleaners.
10. You mention you are putting in a new kitchen. Before you put the new wall linings on. make sure you have nogs in the right places for fixing both floor and wall-mounted units. When you fit the new Gib, mark where those fixing nogs are with pencil. Whoever fits the kitchen will love you for that.
oh, the Ceiling is also to be re lined.. I'm thinking i wont remove the old stuff, But just re line over top - is that smart or not? The ceiling needs to be done as the room next door (which is being made into one large room) has a textured ceiling, where as the kitchen does not... so I don't want the join to look silly so new gib board is probably best
Do it once, do it right. Completely remove the old ceiling, and replace with new.
Hopefully others can add some hints to, so I can learn a bit more.