I think it is a bit unfair that these very intrusive pests get attributed to cheaper places like guesthouses and hostels because honestly, there presence has nothing to do with how much a place costs and even less to do with cleanliness of the establishment.
These little bugs thrive in any environment, expensive or inexpensive. I think the reason why it gets attributed to cheaper places is because if a cheap guesthouse gets infested, the probably don't have the funds to get rid of them whereas a hotel or especially a hotel chain definitely would and they have steps in place for handling something like this.
I have stayed in a lot of places that had bedbugs and while I am not terrified of them like other people are, I would rather not get munched on while I am sleeping so here are a few things to look for if you are checking in to a place and want to make certain you don't get some unwanted travelers coming along with you.
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While they are called bedbugs they don't necessarily live exclusively on beds. Some of them set up shop there and normally they will do so in the creases on the mattress just like pictured above. It is a common practice in guesthouses to allow guests to visually inspect rooms before they decide to stay in them and one thing you should look for is this area of the bed, particularly towards where someone would put their head.
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Even if you don't encounter any actual bugs look for little black dots in and around the seems of the mattress, if you see some dots, this is almost certainly bedbug poo because unlike other animals, bedbugs actually do "shit where they eat."
The creatures are often microscopic or see-thru while young and before feeding. They only become larger and red once they have consumed blood and if you are like me, you would probably prefer that this blood was not coming from your own body.
If you do encounter this on the mattresses it is probably a good idea for you to stay somewhere else because the reason why these insects are so feared is because they tend to travel with people in or on their luggage. If you somehow manage to transport them back to your home after you are traveling, god help you. These little bastards are damn near impossible to eliminate on your own and very expensive if hiring a company that guarantees their removal.
If you do find signs of this please don't be a dick about it and try to alert everyone else in the guesthouse. Often the owners don't really understand what they are or are unaware of their presence. It would probably be a good idea to quietly let them know so they can at least try to do something about it before it gets out of control.