The obvious starting point is to lay the first row of tiles along one wall.
This is fine if your walls are straight and square, but most aren’t, particularly in period properties.
If this is the case with your home, you either accept that the tiling won’t be perfect and continue anyway, or you ‘square’ the room, which means measuring out straight lines to tile along.
Consult a good DIY book or website about how to do this, such as the floor-tiling guide at www.firedearth.co.uk
Apply the adhesive with a notched spreader according to the manufacturer’s instructions, ensuring that you use enough to embed the tiles properly.
Cover about about 1sqm (less if the tiles are small) at a time, otherwise the adhesive may begin to set before you’ve laid the tiles. Regularly use a spirit level to check that the tiles are level, and make any adjustments while the adhesive is still soft.
Ensure that the tiles are firmly embedded in the adhesive by pushing them in place with a side-to-side motion.
Put plastic tile spacers horizontally between the tiles, so they’re evenly spaced. If the spacers are a similar depth to the tiles, it’s a good idea to put the spacers in vertically (sticking up) and then remove them before the adhesive has set hard. This means you won’t see them through the grout.
You usually have to wait 24 hours for the adhesive to set before grouting, during which time you shouldn’t walk on the tiles in case you move them.
Some products allow you to grout sooner, which is great if you’re tiling your only bathroom.
Push the grout firmly into the joints with a grout squeegee (ready-mixed grout usually comes with one of these), and fill in any holes later.
For mosaic tiles, use a grout float to smear grout over the entire tile, rather than trying to do the joints individually.
Leave the grout to firm up for a few minutes, then remove any excess by wiping diagonally (so you don’t dislodge the grout lines) over the tiles with a sponge.
Leave it too long, and the grout will be hard to shift; do it too soon, and you might take off too much. Keep washing out the sponge until all the excess grout has been removed. A lot of stone tiles need to be sealed with tile sealer before you grout them - ask the manufacturer or retailer if in doubt.