A lot a lot needs to be done before purchasing any cloth for making a bespoke suit or a jacket. There are questions such as, how is the suit will turn out to be and on what events or occasion will you be wearing them? So, one should make sure that you have answered all these questions in your mind before proceeding to buy a fabric for your bespoke clothing.
Some of these question in general are:
When and where this suit or jacket/trousers are to be worn; just to the office or any other special event?
What would be appropriate in general with the colors, patterns and material type?
Should be heavy or light?
Will you be wearing it around the year or just exclusively for winter or summers?
How will it match or stand in contrast with your shirts and ties?
Once you have answered these questions in your mind; you can then, directly communicate all this to your trailer or the salesperson from whom and where you are considering to buy the fabric.
Now to give an exact idea to your tailor, you can do two things. These would be wearing something which is identical to the fabric that you want or by collecting pictures of the fabric which you have in your mind. This in an instant would help the tailor realize, what kind of material you want for your suiting.
Now deciding to buy a fabric, keep few things in mind, as to what type of fabric will best suit the season and environment around you and how will you carry it off on daily or weekly bases. This simply means that you happen to live in humid and warm region of the earth then, make sure that the suiting fabric has a slight loose weave pattern. This will make the fabric quite breathable and easy not wear in summers. Then also look for its weight, whether you want it to be heavy (good for winters) and last but not the least, its texture. Whether you want an ultra-smooth, super fine fabric or a tweed type of fabric which is best for winters.
Lastly, look for the patterns or designs that you want to have in your most desired suiting and go for it. Compare the clothes with one another and see what goes best for you. Never make hasty decisions in buying clothes, as this can amplify or diminish your overall personality.