Preparation and planning are crucial if you want a successful shoot. Whatever way you look at it, planning a shoot has cost you, in money and certainly in time, so it makes sense to get everything possible out of it.
There is nothing wrong with using natural light. After all, it is free, but it is also unpredictable and that is something you have little control over. As a result, flash is a great option. You could use a flashgun mounted on a stand with a modifier of some sort to create a nice light. There are certainly plenty of accessories available.
As for lenses, for portraits and short telephoto is about perfect, giving a good perspective as well as giving a comfortable working distance between you and the subject.
Some portrait shooters like using a tripod even with flash, and that is worth considering, especially if you like to tinker with the lighting regularly. Many photographers, however, just handhold so you have total freedom of movement and that allows faster shooting too, which can help give a more fun sessions for you and the model.
The first thing you should do after the model is booked is think up some ideas. This is not easy for most people so just 'borrow' ideas from the plethora of fashion magazines that adorn our newsagents. You might not have access to the expensive frocks or watches but you will definitely benefit from ideas about lighting and posing. There is no shame is taking someone else's idea and developing it further and putting your own 'stamp' on it.
After that you need to get your 'studio' organised. You could always hire one, but a decent-sized living room can be used instead. Backgrounds can be paper rolls or cloth backgrounds.
Then it is onto the lighting. Clearly the set up you use is going to be down to what you own or can borrow. An amazing amount of effects can be achieved with two flash units, but one is a good start if budget is limited. Two heads, a few reflectors and you are in business.
Ideally, shoots should be free-flowing and fun. The reality, however, is that there is lots of stopping and starting and there is nothing wrong with this. The usual advice is to keep up a stream of banter too.
Some photographers can banter, some can't. The best advice is to be yourself and be concise with your posing instructions. Acting out poses also helps too if you are that sort of personality.
A good shoot will fly by and you will soon be pining for more.