Indications of the presence of bed bugs can manifest in a few different ways. You may see the actual bug crawling on your bed, couch, walls, floor, etc.
At times, you may not see the real bug because it tends to feed at night and hide during the day. If the bug is, in fact, feeding at night, you may wake up with bed bug bites. These marks tend to be red welts on the upper portion of the body (from the waistline up) and can appear as a row of bites instead of one single bite.
Everybody reacts differently to bug bites. With certain people, a bed bug bite may not appear directly after the bug feeds or possibly not appear at all. In a situation where you have not seen a bug or received a mark, you may still see bed bug fecal material. Bed bug feces show up as small, black dots or smears wherever the bedbugs are resting (on the mattress, box spring, headboard, etc.).