This is an interesting question, thanks for asking it, and congratulations on deciding to travel. Personally, I find travel very rewarding.
I am not sure if you are looking for a hotel, guest house, or resort, and possibly you have not decided yet. When reading through reviews, see if any mention kids or drunk younger people. I've read countless reviews of hotels I am considering where people mention how accommodating the hotel was to their kids, etc., so that can be a hint that other people will bring children. I've also read reviews of places, for example beach hotels and guest houses in Phuket, that complain about too many drunk young Australian guys, so that is a clue that the area is one where being somewhat drunk is expected.
I don't know if you want a place where you can be left alone, or one where you are likely to meet people. There are many places where one or the other is more likely. Most large hotels cater to single people, and you will be left alone if you want that, or can hang out in the hotel bar and have a better chance of meeting someone. There are resorts with communal dining where you will have a good chance of making friends. At more isolated resorts (further from a town) you will likely see the same people all the time, which may make it easier to make friends or join people for group activities, if you want that.
If you are looking for intimacy, there are singles resorts where other single people will be. If you are gay, bisexual, or unsure, there are hotels, resorts, and guest houses that will be especially friendly and welcoming.
Wherever you decide to go and stay, I am confident you will enjoy it.