There are many parameters to consider. The goal here is not to make an exhaustive list but to give a kind of charter for any project of solar installation.
First, be sure that solar energy is well suited to your needs. To simplify your solar system, we can say that this energy is more suited to a reasonable but steady demand, for example, solar power a small house in hot countries with lighting, sound, TV and a small cold. However, it will be very difficult to produce enough energy to professional needs like workshop or bush even two hours a day.
If you think this is the energy you need, so here we go !
If you have a tin roof to do a solar system, it is necessary, in hot zone, to leave a gap between the plate and panels. Indeed, when the panels heat their performance decrease. This also has the advantage of isolating your roof and your home will be cooler. A gap of 40cm is convenient for installation and connection and allows effective ventilation.
Now that you know where to place them, orientation plays a very important role. And then I ask you not to believe everything you read on the internet.
You will see very often that solar panels must be turned to the south ! This only applies when you are located in the northern hemisphere (a nothern country) that is to say above the equator. If you are in a country south of the equator so they should be in the north !
Then comes the angle, your panels should be perpendicular (90°) to the sun the month when days are shorter to produce as much as possible the lowest month.
You can also choose another angle optimized for the month when you most need this energy (instead of seasonal work)
It is also possible to use a tracker, a device that tracks the sun. An automatic tracker is expensive but a manual tracker can be made with very little things and you will increase your yield of at least 25%. However, we must be sure that the person in charge to follow the sun will do because if he doesn't, there is more to loose than to win ! This solution is the most suitable when it is the owner who cares.
This type of solution can be made quite easily, if you're interested, a plan is available on request.