Cutting tiles with nippers is a skill that comes more from practice than from instruction. Both the nippers and the tiles have unique characteristics & so it’s impossible to provide advice that works every time on all tiles.
Below, I’ve illustrated my approach to cutting a difficult shape in the hope you can apply some of the ideas to your own work.
Start by cutting up to and around the most difficult point – the apex of the triangle.Keep your nippers angled away from the traced area – it’s better to do more smaller cuts than to try and take away large chunks.
Roughly cut off all the surplus tile up to about 5mm from the line as shown.Cut roughly, but take care your tile nippers never angle towards the lines – the thinner the shape, the more it will tend to break if you angle your nippers toward the traced area.
Always start with the trickiest parts – in this case it’s the apex of the triangle. I’ve started by cutting away 20-30mm along the line very carefully and gently.If this part can be shaped successfully, you’re unlikely to have any problems with the rest of the shape.
Going with the thought – trickiest bits first, take the concave curve out. Start from the corners (this is important), and slowly nibble tile away up to the line.Parrot beak nippers are better for this section if you have them.
Once you’ve got the curve & the apex, the rest is pretty straightforward.Continue working only small pieces though – if you cut too much, you’ll need to start again.
To finish your piece off nicely, it’s worth running a tile file along the edges to take out any bumps or jagged bits.
If you have trouble cutting shapes in one piece, and run out of tiles, you may have to break all the pieces into shards and reform them as shown.You still finish up with very accurate, consistent shapes, and your work will still look great. Sometimes you might prefer to break your shapes up like this anyway!