I haven't had foster children myself, but my parents did, and I grew up with one who did not get adopted and one who did. My sister has also adopted three foster children, so I have a bit of non-parental family experience with it.
Do you have any biological kids?
Do you have a child in mind? If not, some things you might want to consider are history and age. A lot of foster parents are more comfortable taking in children who are younger than their biological kids, because they will have previous experience with all the "normal" stages that the new child goes through. Believe me, any foster child will have enough other issues that the fewer "normal" surprises the better. Also, your own kids may be more understanding if the new child is younger.
Think long and hard about what kinds of problems you are willing to deal with and what kinds you are not. Are you able to cope with the problems of a recovering drug addict or a person with a tendency to steal or set fires? Are you able to deal with the special issues of a child who has been physically abused? Molested? Every parent has different hot buttons, and you might be able to cope with one kind of challenge but not another.
Once you have a child placed, bear in mind that the case file you saw is probably not complete. It is very difficult to gather a complete case file on a child, especially one who has had multiple placements. Be aware that you might find yourself dealing with things like Attachment Disorder, and if so, you will need immediate support. Get it! Use whatever counseling services the state might offer, and join online or in person support groups. Whatever you go through, I guarantee someone else has gone through it and maybe has solutions you haven't thought of.
I know, I may have made it sound very negative... and sometimes it is. But there are also lots of rewards. When I see all the healing my little nephew has gone through since being placed with my sister, it just thrills me. No matter what he's been through, this kid has spunk that will not die.
The challenges are hard to predict, so I've given you a list, and you probably will not encounter them all, but likely will encounter some. But offering a good home to a child in need is a truly good thing to do, and it can be very, very rewarding.
---Christina