First and foremost, compose and compile a list of must haves and priorities for your bathroom, calculate the costs and match it against the estimated budget and get ready for comparatively cheaper alternatives if things don't exactly wrap up in your plan. Decide if you will keep the existing plan or rearrange or expand it. Options for expansion include adding a bump-out or commandeering space from an adjoining linen or bedroom closet, for example. Seek professional help if you are adding a new bath or expanding an existing bath.
Possibilities include architects, general contractors, design/build firms, bathroom designers, and home improvement centers. Take the help of design software in the market that will help you simulate the design plan on screen. Most of the bathroom planning software come with readymade templates that help you choose the best plan for your bathroom size and your budget, you can also optionally add accessory widgets to simulate the over look. Next, consider the time frame of the project execution and also consult with design experts on your bathroom plan before you proceed.