Use lines of at least .25 to ensure that they show up after printing. Letterpress is a more advanced process these days, which means it can print thinner lines more effectively, but avoiding hairlines ensures that the printed design will look perfect.
Letterpress printing traditionally uses up to two spot colours and will be more expensive if more colours are used. Designers are free to use up to four colours in their design, but it is expensive and may not be necessary.
One of the strengths of letterpress is its ability to print colours at 100%. For lighter colours, designers should use a separate, lighter coloured ink rather than a screen. Screens work better with offset printing.
Letterpress is ideal for printing type but designers should aim to keep font sizes to larger than 6pt to get the very best result.
Crop marks should be used during the design process to ensure that the whole design comes out during printing. This is recommended for most types of printing, as designs created up to the trim line have a tendency to be cut awkwardly.