1) Get a plumber involved!
Ensure an experienced and reliable plumber visits your home before committing yourself to anything. You should be given a free initial quote to help you budget your project. You also need to verify your system's compatibilities.
2) Get the correct measurements.
Every inch makes a difference! Buying a shower enclosure or a freestanding bath that does not fit in your bathroom can be very difficult to tackle.
3) Check your water and plumbing systems.
Sometimes, systems can be incompatible with specific bathroom products. The last thing you will want is to commit to a product that won't work in your home! Unexpected incompatibilities will result in big headaches.
Ask the plumber a lot of questions about your water pressure and anything you may not understand. A good plumber will be happy to clarify your doubts as well as guide you through different products.