funny you ask, because i happen to be a bit of an expert in that field.  
let’s not waste any time on small-talk – we’ve got some Serious Money-Saving Hair Business to get down to!

1.  you know that thing they do every time you leave the hair salon?  the one where they say, “so we’ll see you in 4-6 weeks, right?  how about we just book that next appointment right now, since we fill up so fast…”
well, that’s a lie.  (usually.)  i worked in a pretty upscale salon for a year when i was still in nyc, and even there, under most circumstances it was possible to book an appointment with your favorite stylist about a week in advance.  (i mean, if this is your wedding day hair style were talking about you might want to call more than a day ahead, but otherwise…  hold your ground, soldier!  don’t let them bully you into committing to shelling out another $30, $60, $150, or whatever it is your stylist charges every four weeks.)  

2. (this ties in with #1…) take some time to find a stylist you love.  
someone you trust, who really “gets” not only your look, but also the texture of your hair.  this is super-important.  and unfortunately, most often found at the higher-priced salons.  the up-side of this though, is that with the right cut, you can easily go two, 3, even 6 months between visits.  hair doesn’t grow that fast, and in most cases it takes a few weeks to stop looking “freshly butchered” and grow into it’s full potential.

3. experiment with hair accessories.
even when you know you’ve pushed it way past “acceptable,” you can usually get a few more weeks, (ahem…  months?  stop staring at me.)  out of a ragged ‘do by clipping it up, pinning it back, twisting it around something, knotting it, braiding it – and if all else fails, i heard the turban is making a comeback. 

what if – like me – you are morally opposed to bling in the weave?
pick an accessory that’s small, tasteful, and similar to your hair color.  check it:

this is a fine example of what i like to call a ‘totally classy hair-piece.’  
it also happens to be holding some Very Angry Bangs back while i procrastinate getting a trim.
you can find more totally classy hair pieces by clicking on the picture.  or here.  i dare you.
bonus: they’re a total bargain, and made by the sweetest etsy-er ever.

4. ask about (free!) fringe-trims between visits.  
most salons at the mid-to-nice end of the spectrum offer complimentary bang trims between visits.  (of course you still want to slip your stylist a little “thank you” cash, but that’s nothing compared to the standard 20% on a full-priced haircut.)  getting your fringe trimmed between cuts will do wonders for  hairs that seem like they’ve grown past the point of acceptable.  unless you’re doing something drastically short or super-shaped, no one’s going to notice if your sides are half an inch longer than they normally are.  this leads me to #5:

5. trim it yourself!
i’m serious.  i’m also serious that there are some pretty big rules that go along with this advice.  such as:

• take time.  this is not something you want to tackle when you’ve got 5 minutes to get out the door for work.
• don’t cut more than 1/4″ in one snip.  you can always keep trimming.  unfortunately, (i’ve learned) you can’t glue that stuff back on once it’s landed in the sink.
• cut it dry.  never EVER trim when it’s wet.  hair “shrinks” up once the water-weight isn’t weighing it down.  i’m not kidding.  don’t do it.
• do not combine this activity with wine consumption, tequila shots, beer-bongs, or any other methods of alcohol ingestion.  ”hair-cutting” and “party atmosphere” do not belong in the same bathroom.  even if it’s just a party of one…
• same goes for “emotional turmoil.”  if you and the boyf just exchanged a few unfriendly words, this is not the time to pick up the scissors.   turn to the beer bong instead, ok?
• oh, and use hair scissors.  they don’t have to be expensive ones, but come on, we’re classy ladies (and lads.)  do we really want to trim our hair with the same scissors we just pruned the ficus with?  no.

6. preventative maintenance.
don’t shampoo every day.  this is incredibly damaging and entirely unnecessary.  trust me, i have that lucky combo of baby-fine locks and hyperactive grease glands – (is that what they’re called?)  i will be retiring the day they develop a car that runs off of sebum.  but in the meantime, i’ve learned that my hair is much much healthier when i rinse it every day in the shower (and even use a vigorous scrubbing motion, which helps distribute the oils more evenly,) but only shampoo every 3-4 days.  same goes for using heat tools – if you must blow dry, aim at the roots and spray the ends with a heat-protecting product.  combining these two will almost entirely eradicate split-ends from your life, which means, “hair cut what?!”  
(throwing in a little deep-conditioning treatment every once in a while doesn’t hurt either…)

see?  i just saved you a ton on your hair expenses.  that’s more than that geico lizard can say…

Yay, Diana!
For more cheap-as-free hair and beauty tips, here is another amazing PainfullyHipster post by the lovely Mary Catherine about spending pennies instead of hundreds on better beauty products.
-Amber