Choosing the kind of hot tub deck you need is as much about personal preferences as about practical considerations. There are many ways you can go, and the only real limit is the available space, your budget, and your imagination. Here are some of the options (but by no means all).
If you have a stand-alone hot tub, you can build a deck around it or forego one altogether. Many users of this type of spa choose what's called a 'rim deck'. This consists of a wood or plastic shelf that surrounds the top rim of the tub, either all the way around or part of it. Depending on its strength, this type of deck can simply be used for resting your drink and your towel on, or it can actually be stepped on, on your way to the water.
At the other end of the spectrum, you may want an elaborate gazebo deck for hosting large parties with the hot tub as the focus. If you throw outdoor parties for sizeable crowds on a regular basis, this is a good option (assuming you have the means). The gazebo's roof will provide weather protection from the storms that seem to blow up out of nowhere during the spring and summer months.
As an in-between measure, you can build a deck to accommodate smaller parties, with room for a few chairs, a table or two, maybe some benches, and a nice railing. This is a great idea if you have a larger hot tub that you share with friends on a regular basis. Some folks will want to stay in the water for virtually the entire time, while others will choose to get out to cool off, grab a drink and chat tub-side. You'll find that your deck will ensure that your visitors enjoy their experience and will want to return more often.
Most hot tub decks are made of a durable wood - oak, pine, redwood or cedar. Cedar is the most popular. It looks beautiful, requires very little maintenance, and produces a pleasant aroma, especially when it gets wet and the temperature is warm. It's ideal for hot tub decking.