Grammar usage

Agreed with Tolley, and please note that each one has a slightly different meaning:

If I had known his number, I would have given it to you.

In this one, the (possible) action takes place in the past. I didn't know his number, but if I did, I would have given it to you.

If I knew his number, I would give it to you.

This one takes place in the present, where I don't know his number.

If I know his number, I will give it you.

In this one, the (possible) action takes place in the future. If I find out his number at a future time (and it's implied that I may or may not find it out -- both are possibilities), I'll give it to you.

Reference interview is a process of asking question, paraphrasing and providing information. Reference interview starts and ends with the user. The librarian should be always approachable and greet the client. Shows interest and is active listener while client explaining the query. Felder - Silverman (2009). Explains that "they work well alone or in a one-on-one situation with another person and when given the opportunity to devise theories". Allow  patrons to talk and   him/ her to complete the question. Supply them with paper and pen to explain their requirement if required.  Librarian listen carefully, write it done what he has told, think about it  and paraphrase and repeat it.  Explain what she has understood using flow chart or diagram or picture.   Give patron a chance to give more details or say yes or no. if it yes go head. Ask patron,   which format  of resources prefer e-book, article, video or CDs. Find a term to search and turn  the catalogue screen and explain how she is searching. Knoer, S. (2011, p. 4) states that "our job is to translate their question into a question that we can use to search, something with terms that are useful - for us". Ask him whether used online public access catalog (OPAC). Show the search results to check whether she/ he is expecting the same thing. If yes, then write down the call number and the title. Ask client "would you like me to show you how to look? If user wants help go along with him and explain how the call number works and grab the resources for him/her. If you need more help or is there anything else I can help you out.