I know the feeling when you want to set up your own studio so you can record at home but you have to decide where in the house to have the setup. I will give you some suggestions and some of the things to consider for each place.
There are a number of places that are often suitable for a home studio but it will depend on how much equipment you want to use and how much space you have in each room of your house.
A bedroom is a good place for a studio and if you have a room not being used for anything else this can be the ideal place for many reasons. Most bedrooms are already weather proof so you don't have to think about any protection for your equipment from rain or dampness in most bedrooms which is something that makes it a very good location for electrical equipment. If the room has no windows then covering them with soundproofing material may be necessary to maintain a quiet recording space but the bedroom is a good place for a private small recording studio. If your setup will be computer based and your equipment will not span much further than the space of an average work desk then a bedroom if the option I would recommend. You will need space for instruments if you will be recording with them but event with that in mind most bedrooms are enough to start with.
Sometimes you may decide to share your recording studio with other people and this is something to consider because if people need access to your home so they can enter the studio it could be uncomfortable for other people living in the house to have their privacy and living space interrupted by people there to use your studio. If you will use your sleeping room or a room used by other people living in the house then the bedroom may not be the best option but I suggest you talk to everybody living in the house about it and come to a mutual agreement about it.
Bedroom recording studio tips:
A garage is a good place to set up a recording studio and is often used for rehearsal studios. If you do not have a bedroom that can be used then the garage is a good place. There are some considerations I would suggest you consider if you want to put a studio in your garage such as dampness and security. A garage is designed for cars and outdoor equipment which may not be the ideal place for electrical equipment so you may need some extra damp proofing depending on the design of your garage. You will also need to consider security because all that stands between your valuable recording equipment and the outside world is your garage door and your equipment may be a potential target for burglary. You can use a cheap home security CCTV system to monitor access to the garage studio but it is something to consider before having expensive equipment in the garage.
Garage recording studio tips:
If you have a detached apartment on your block of land such as an unused guest house or granny flat then this could be the best place to set up your home studio. Similar to a bedroom studio and garage studio this has advantages and disadvantages but a big advantage is you can make it into the studio you want without effecting the rest of the house. If the building has windows they may need to be sound proofed and you will need to be sure that you have sufficient power outlets and the building is secure enough from intruders and also safe to store and use electronic equipment.
Detached building recording studio tips:
If you are only going to record occasionally you may want to consider having a computer only based setup and using your personal computer for recording. This will not require a lot of space and can be in your living room or entertainment area.
I hope this gives you some suggestions and things to think about when deciding on the best place you build your home recording studio. The best place will always the place that suits you and everybody living with you and meets the needs of your recording ambitions.