Always ask your potential references before sharing their names and contact information.
They'll likely agree to be a reference, but it's possible that they have already agreed to be someone else's reference for the same position and may need to decline.

Assume that when you enter a recommender's name into a form when you're applying, they will immediately receive the request for a reference. 
Ensure that your references are not caught off guard or at a time that they cannot help by informing them in advance of your application.

Make sure your recommender is 100% prepared to answer questions about you and can represent you well.

1. Send your recommender PDFs of the job descriptions - not links to the descriptions online because links break.
2. Provide copies of your resume and any personal statements you need to write.

This allows them to tie everything together and create a consistent picture of you for whoever is on the other end of the letter or phone call.

If you need a letter:

• Please give your reference at least two weeks' notice when you ask for a letter—longer is even better! Unfortunately, schedules get hectic, and pressing issues occasionally arise. Your letter writer needs adequate time to write a letter that represents you well.
• Let your reference know what you hope to get out of the experience or position that they are recommending you for. It's one thing to write a letter recommending you for something, but it makes the letter better if your recommender can tie it to your overall goals.

Finally, please let your recommender know how it turns out! :-)

Amanda I.'s advice:

Go with someone who can speak to how you meet/exceed the qualifications. Former and/or current supervisors are a good choice as they can expertly discuss your work. If you feel that your profs will be able to explain what needs to be explained to the search committee, feel free to use them! If you were going into academia - like to a PhD program - you'd definitely want a professor as a reference.

Alicia's advice:

I definitely second everything that Amanda just said.  When I was selecting recommenders, I also thought about how my work responsibilities and behaviors that my recommenders had observed related to the job(s) I was applying to--for example, if I was applying for a job that was heavy on instruction, I asked someone who had observed me teaching.  I also considered who might know (or work in the same circles--not hard in the New England library world!) as some of the folks where I was applying.  As a final tip, make sure you cultivate some good relationships and potential recommendations in a variety of places where you've worked, interned, or volunteered.  When I applied for my current position at URI, I had to abandon two of the three people whom I usually relied upon for recommendations because they were on the search committee.

Peter's advice:

I also agree with the above. You want to find people who can speak to the specific qualification of the position. I not only give references; I also contact a lot of references, and sometimes Reffie candidates use family members or friends (not great), supervisors from non-library jobs (sometimes the best you can do, if you haven't had a library job, and often quite useful), or professors (sometimes OK, if they have a good sense of library work, but they can't often talk about job duties well). Sometimes, however, you need to go with who you can line up. For future reference positions, Amanda or I are good picks, for teaching, Alicia or Mary might be better. None of us will feel slighted if we aren't asked.

Amanda I.'s advice:

One might hope that the process will be quick and also allow time to make moving preparations, if necessary. In reality, some searches go extremely quickly, while others drag on.

One librarian here sent a resume and cover letter for an academic position in November of one year, had a phone interview in December, and finally heard back in April of the following year. Longer processes have also been reported.

That said, if you are interviewed, feel free to ask what the timeline for the search is, and you can even ask how many other applicants they're interviewing, to get a sense of what the landscape looks like.

More tips from Alicia:

When I was getting started, I was told it generally took from 3-6 months from applying for an academic librarian position to starting it--which has generally been the case in my experiences (although it can be shorter or longer, as mentioned above!).  When I was applying to academic librarian positions, there were often flurries of job openings followed by "droughts" with very few job openings in the area.  Because of this, think carefully about your timing.  It's okay to start applying as you're finishing your degree (just note your anticipated graduate date in your cover letter).  Post-MLIS internships can be a great way to get extra experience, but they can also interfere with your ability to apply to, interview for, or take a full-time position.  There's no one right answer for everyone, but make sure to consider all your options and prepare yourself for different scenarios, just in case.  

From Amanda C-E:

I totally agree with Alicia's assessment that there can be flurries of job openings followed by long gaps. It would be wonderful if academic libraries followed a consistent hiring schedule, but, alas, they do not! In my hiring cycle, those who started applying November/December of their last year of the MLIS had a job lined up and finalized prior to graduation, while those who submitted applications in February/March/April had application experiences that weren't finished until mid-summer. For some, it may be important to know early on where you're going to land (if you're coordinating with a partner or have financial pressures that mean you need to avoid a gap in employment). For others, taking a month or two break between grad school and the first library job may be a higher priority. I would recommend thinking about what you need and deciding when to apply accordingly. 

It's never too early to start getting organized for the application process!  It can be easy to lose sight of the big picture as your complete your coursework and juggle various part-time jobs, internships, volunteer opportunities, and other responsibilities.  When I (Alicia) was between the first and second years of my MLIS program (back in 2015 when it was a two-year program), I started getting a little overwhelmed by the variety of jobs I was working, worried that my experiences would be scattershot and not come together to qualify me for any professional position. 

To get a better grasp on expected job qualifications and my own experiences, I surveyed a variety of current job postings related to instruction, reference, and digital humanities (my three focal points of interest), and I created a list of all the qualifications and preferred qualifications, organizing them by themes as well as frequency.  I detailed how I'd met qualifications and brainstormed ideas and timelines for meeting unmet qualifications.  

This process was immensely helpful in staying organized because it highlighted what I'd achieved (and how, which was useful info as I started compiling application materials!) and helped me prioritize what experiences I should still try to gain (e.g. why focus on something that was only listed in one job posting if another qualification I had yet to meet was mentioned in 7 postings?).  

If you think this process would be useful to you, here is a copy of my original 2015 document to show you how you might start a similar survey of your own that is more focused on your own professional interests.