Signal phrases introduce the ideas you want to use from another source. These ideas can be the actual words which you take from the original text (a quotation) or a restatement of these ideas in your own words (a paraphrase). Signal words can be very simple (states that …, writes that …). They can also indicate your opinion about the writer’s ideas (argues convincingly that …). You, at least, were convinced by the writer; other readers might be less persuaded.
Here is an example:
Freebody and Anderson suggest that "cohesion, in the specific sense of linguistic ties, simply is not very important in reading" (1983 p91).
"suggest that" is a typical signal phrase. A signal phrase introduces an idea (or a proposition, argument, rebuttal etc.) which the writer found during her research. In this case we have a quotation. These are the exact words found in that particular article in that journal indicated in the citation and which you can find in the bibliography.
The word "suggest" was chosen by the writer who found this quotation during her research. She could have used other words (claim, state, argue ....). But you should choose your signal words carefully; they can give clues about the information presented in the quotation, information about the writer's stance, and clues to your attitude to the information in the quotation.
We could also rewrite this in the form of a paraphrase. For example: Freebody and Anderson (1983 p91) suggest that, as far as linguistic ties are concerned, cohesion is not of much importance in reading.
The signal phrase makes it clear that the comment about cohesion in reading belongs to the writers Freebody and Anderson.
There are many verbs which can be used in signal phrases but there is a limited set in common use. These are the ones you are most likely to see (or need to use):
acknowledge, add, admit, affirm, agree, argue, assert, claim, comment, conclude, concur, confirm, declare, demonstrate, deny, emphasize, explain, find, hold, hypothesise, imply, indicate, insist, maintain, mention, note, observe, point out, predict, propose, reason, reflect, remark, reply, report, respond, reveal, say, show, state, suggest, theorise, understand, verify, write