Discussions about wedding costs should be held at an early date and in an open fashion. A firm decision on a realistic budget will smooth the wedding planning.
Nowadays, there is no strict etiquette on who pays; every situation is different and the individuals involved must honestly discuss and establish how the wedding will be funded.
It's best to spend money on the things that will have the most impact, such as the venue, the dress, and a free bar. The details, such as wedding favours or extra decorations, can be added later on if there is sufficient budget left.