OK, sorry for the delay.
1) Work out where your first tile is going to go in terms of left anf right. Every other tile will fall on the wall relative to this first one - basic rule is, you want to make sure of two things:
i) That the last full column of tiles moving towards each edge of the wall finishes far enough away from the corner so that the cut tiles (the ones actually tucking into the edges) are of a decent size - you don't want to be shaving a tiny bit off a full tile, or making tiny slither cuts all the way up the left or rigt side of the wall
ii) That the cuts around the window reveal (vertically) are of a decent size too, for the same reasons as above.
A simple method "to try" would be to mark the centre of the reveal and try the following two arrangements
i) line the centre of a tile with the centre mark on the reveal and see where your cuts will fall
ii) if your cuts are a bit slim, frame shifting the whole lot across half a tile, i.e. line up the edge of your first tile with the centre line on the reveal. See where your cuts fall now. Remember, you need to be thinking about your cuts up each side of the wall and also up each side of the window reveal.
If niether method gives you acceptable cuts, try shifting the whole frame along quarter of a tile - less desirable, but practicality should prevail over aesthetics when it comes to DIY if i) and ii) dont work.
2) Once you have established the positioning of the first tile right and left, you need to repeat the same procedure moving from top to bottom. Your aiming for decent size cuts at the top and bottom of the wall and also at the top and bottom of the reveal. The procedure is the same as above.
You can make a gauge rod to help show you where your cuts will fall - a piece of timber with several tiles and grout lines marked on it. This can be slid from left to right and top to bottom. REMEMBER - you should know what size cuts (roughly) you will have all the way around the edge of the wall and the reveal before you start.
3) Once you have the starting height on the wall established, fix a batten horizontally at this level and work from there. Mark your first tile (left to right) on the batten and away you go. Fix your full tiles and give yourself a vertical column of tiles all the way up passed the top of the reveal. In your case, this will only be on the left side of the reveal as you will have cuts running up the other side of the wall, unless you're using really tiny tiles.
4) When it comes to the reveal - you need to establish where the reveal is its smallest top to bottom - looking at the spirit level, its likely to be on the left. When you have worked this out, mark your first cut tile so that it runs a few mm passed the bottom of the reveal at this narrowest point. Mark all the other tiles running across the bottom of the reveal the same size as this one. You want a cut line of tiles to all be in line with each other running across the bottom of the reveal. If the reveal runs out a lot, when you look at the back of the tiles you have just cut and fixed, you will see the reveal running out. Now cut a small piece of trim and slide it down behind the tiles and then slide it from the corner of the reveal to the other. This will clean out the adhesive in that area and will give you time to fix the rest of the tiles before fitting trim. If you dont do this, when you come to fit the trim later, it wont slide in because of the dried adhesive.
5) Repeat this process for the sides of the reveal.
6) If youre only tiling halfway up the wall, you will need to run trim across the top row of tiles and will need to externally mitre it into the reveal. You can buy 3 way corner trim blocks that fit on the corners of the reveal and you just run your trim up to them. Probably better than a dodgy 3 way mitre.
Hope this helps.
Will
