Hug is closest to the mark, I'm a pro tiler/bathroom fitter so hope I know what I'm doing.
1-Fit the bath level ( the fall is pre set in the base so no need to allow one) and flush up to the wall (chop brackets in BUT don't chop actual bath rim in unless out of square).
2-Silicone between wall and bath BEFORE tiling.
3- Tile away, baths are hardly ever flat so bear this in mind when setting out. allow a 2mm gap between bottom tile and bath (to allow silicone somewhere to go.
4- Half fill bath with water to add some weight and deflection Silicone (using low modulus sanitary grade silicone)
5- Grout. (silicone 1st allows a good waterproof seal to form, if you get grout in joint 1st it's difficult to get a nice seal.
6- DON'T under any circumstances use those crappy plastic/rubber bath seals down to the bath. the never seal and look lousy.
7- Stand back and admire handywork.