Pencil
You would be surprised how often you use the trusty pencil when you are tiling -- making notes and measurements and marking starting points. The one weakness with pencils is that they aren't great for marking the top of a tile. For this, a china marker or a silver marker pen is recommended. Chalk is also useful for marking lines across a floor and providing your guide for laying your tiles.
Protective Clothing (Goggles and Gloves)
Wear hardwearing clothes that can withstand the work you will be doing. Protective goggles are essential for when you are cutting. Latex or nitrile gloves protect your hands from cement -- cement burns and injuries are a very real risk.
Dust Sheets
Useful for protecting areas that are at risk of damage in the tiling area such as bathtubs and sinks, or even just to rest your bucket and tools on to protect the floor from getting dirty.
Sponges and Cloths
To keep cleaning as you go -- both surfaces and tools. It's good practice to be in the habit of cleaning as you go and not letting any grouts or adhesives set.
Spirit Level
Never assume that your walls and floors are straight. It's a common mistake to start your corner tile in the corner of the area you are tiling, only to find yourself going off at a not-quite-so-straight line. Measure and make sure.
Utility Knife
Cutting tape, opening bags, cutting silicon nozzles.
Tape Measure
For measuring gaps and square meterage -- this should be a staple of your toolbox.
Step Ladder (Wall Tiling)
Consider how high you will be tiling -- always remember to stay safe.
Scraper
Use a scraper for scraping old paint and/or adhesive from walls and floors when preparing your surface to tile on to.
24oz Rubber Mallet
A rubber mallet will help when levelling tiles -- a gentle knock with the mallet helps keep everything level.
Wooden Baton (Wall Tiling)
For support of tiles until the adhesive is set. Just a strip of straight wood that can be temporarily screwed to a wall.
Spacers
These little crosses provide a uniform gap between tiles that is impossible to achieve without them. They come in a variety of sizes and the choice is down to you as to how wide you want the grouting to be. British standard minimum recommendations are 2mm for walls and 3mm for floors; 1mm can be used with rectified tiles.
Adhesive Spreader / Trowel
When sticking tiles to a surface it is important to make sure you have an even covering of adhesive. Use a notched spreader to create a combed effect with the adhesive -- this tells you that the consistency is correct, shows you where you have spread, and the grooves create airways which help the tile stick. Top tip: only spread enough adhesive to do a few tiles at a time, as it sets quickly.
Tile Cutter
Unless your room is perfectly square, you are going to need a tile cutter. Cutting around edges and door frames is part and parcel of tiling. There are three types: a Manual Tile Cutter for straight cuts in ceramic or porcelain (quick and mess-free); an Electric Wet Saw for straight or angled cuts in ceramic, porcelain, glass, and natural stone (water eliminates dust and keeps the blade cool); and an Angle Grinder with a diamond blade -- small, affordable, and very versatile. Always use safety goggles and file down any rough or sharp edges after cutting.
Buckets
You will need a bucket for mixing grout. Make sure the bucket is clean so as not to discolour your fresh grout. A bucket of clean water on hand for cleaning up spills and excess adhesives is also very handy. A bucket trowel is useful for getting the last remnants out of a bucket and for lifting smaller tiles from the surface before they set.
Grout Float
The grout float is designed to make the grouting process as smooth as possible. Spread the grout into the gaps between the tiles with the float. Made of rubber so as not to scratch your newly tiled surface, it is important to keep your float clean to extend its life and protect your tiles -- a hardened bit of grout can scratch a tile.
Grout Finisher
Only really suitable for grout joints 2mm or less. This handy tool is used for getting into hard-to-reach areas and finishing the grouting with a smooth finish. One end is the 'blade' for filling any gaps in the grout joints; the other end is the 'ball' for smoothing out a line in the grout for a professional finish.
Dustpan and Brush
Clean up after yourself and dust down as you go -- small bits of dust and grit can leave the tiled area uneven. A spare hand brush is great for cleaning out excess adhesive from the joints, though you may need to give the tiles a quick wipe-over with a sponge when you do it.