Placement

There are lots of different species used for bonsai and so there are different requirements.
depending on the species you provide the right place to get them growing happy!
some tree’s will do great in full sun while others like a spot with some morning sun but mostly shade for the rest of the day so its advised to do some research on the preference of your species.

Indoor or outdoor?
some tree’s are sold as indoor trees while others are sold as outdoor tree’s but be aware allot of species need the cycle of the seasons and require a period of dormancy to remain healthy meaning in fall and winter they rest to start growing again in spring and summer.
the trees that can be kept indoors are usually tropical species that can not handle cold temperatures and do not require a dormancy period but sometimes additional artificial lightning or humidifying is needed to get to good results as inside there will always be less light getting to your tree then outside and if placed on a window sill above a radiator or other heating source this creates a dry airflow that can be bad for your tree, please realize that an tropical specie will also do better when placed outside during the months that the temperatures do not drop below a certain number.
as example i own a ficus that once temps do not drop below 15 celcius it goes outside on the bench and when the weather cools down i move it inside on a light spot until it can go outside again.

Any other species that is not tropical should always be kept outside to keep it alive!

species like pine and other coniferous type of tree often like a spot in full sun while other species prefer more shade during the hottest parts of the day so again you will have to find out what your species prefer to pick the right spot, next to sun or shade also consider the wind as a factor that can dry or damage your foliage, some species like Japanese Maple have tender foliage that can be damaged by continued strong drying winds.

To help you be successful in growing bonsai its also important to know if the species you have is suitable for your climate some climates have harsh winters or really hot summers so maybe you have to provide winter protection or protection against the scorching sun.
To help you figuring that out there is a hardiness zone map called the USDA zone’s
when doing research on a tree species you often come across the usda zone they are able to grow in so figuring out what the usda zone is where you are located helps determine if you can grow that species successfully.
you can find your own usda zone here