The conditions for using a 把 sentence were briefly mentioned above. These are:

The object is known. (It's already been mentioned or discussed previously.)
The sentence describes what happened to the object in some detail (it's not just a "bare" verb; there's "more stuff" after the verb).

Known object

把 sentences can only deal with objects that are previously known about or have been clearly established in context. In other words, 把 sentences should have objects that are obvious.

This means that the object must either be definite (often preceded by 'the' in English), or generic. A generic object is a general class of things that the listener should know about. For example:

Here 茶 and 咖啡 do not refer to any particular cups of tea or coffee, but to these drinks in general. This is acceptable because as general classes of things (generic objects), these are known and understood by the listener.
Disposal (what happened to the object)

The other requirement for a 把 sentence is that it described what happened to the object, or its end fate as far as the sentence is concerned. This rules out any actions that don't have a clear effect on the object, such as psychological verbs. For example, you generally can't use 把 sentences to describe emotions or perceptions. Something has to be done to the object, and not just done by the subject.

Some examples: 
× 我 把 他 想念。

None of these are acceptable 把 sentences because the object is not directly changed or affected by the verb. There is no disposal. So far so good. But it can get a bit trickier. The object does not have to be physically affected in the real world for a 把 sentence to be acceptable. For example, a 把 sentence could be used to describe something being written down:

Here the name hasn't been physically affected, but it has been converted into written form so its disposal is still described. Another example:

Again, the 'something' in this sentence can't be 'changed' or 'affected' by being spoken about, but it is a change of form so a 把 sentence can be used. Even real world objects that do physically exist do not need to be physically affected to appear in a 把 sentence:

These three disposals are all different types of interactions with an object, but each is a disposal.