There are 4 basic ways in which a spirit or ghost may manifest itself. The one that most people think of but is probably the least common is a visual apparition. For the investigator, catching something like this on film is the holy grail of evidence. In this form of manifestation the ghost or spirit appears in physical form. They may look like a normal, living person, a semitransparent wispy figure, or anywhere in between. Visual apparitions may also be of animals or objects.
The second form of manifestation is through sounds. These may be disembodied footsteps, the sounds of doors opening and closing, music, or speech. Often, in the cases where speech is heard, it is muffled conversations from an empty room and there are many reports of people hearing their name being called. These are of course just a few examples
In the third form, scents or smells are detected. Often times there are reports of smelling flowers or cologne. Pipe, cigarette and cigar smoke scents are very common as well. These scents usually do not last long. Typically, someone will catch a brief smell and about the time they recognize it, it is gone.
The last form is tactile. Like the others this can take several forms as well. A common example is feeling a cold spot in a room. These spots are believed to be caused by a spirit absorbing the energy in a room to assist in further manifestation. Heat is just another form of energy and when used by a spirit can drop the temperature 10 degrees or more. Sometimes it is a small area that is affected and sometimes a whole room. Tactile manifestations can also take the form of being touched, like a hand on the shoulder or a poke in the side. Sometimes hair is pulled or a piece of clothing is tugged on. These are generally very slight but can be forceful in nature.
These different ways a ghost or spirit may manifest may happen individually or together. The combinations are as varied as the hauntings they are associated with.