Ask if you can change the size of your ad to save money.
The best way to save money is to ask whether you can make changes to your custom posters. If you change the size, can your printer be able to print on a much smaller printing press? Is it possible to save on costs this way? This just means that you don't have to print your full color posters for example on a big commercial printing press if you have an A5 sized requirement. Moreover, if you need your custom posters in small amounts, it would be better for you to try out poster printing companies that focus on small print runs rather than get your usual printer to do your job.
Be definite with your print quantity.
“Run-ons” are much better than having your printer make a second print run. Why? Because it'll definitely cost you more. Run-ons are extended first runs according to printer speak. For you to be able to know the difference in costs, ask your printer for quotes on both. This will help you see how much you can afford with your budget and how many will your budget allow for quantity.
Create your own dummy or mock up to make sure you have all the right specs.
Your mock up can help you check your configuration. It can also help you see the actual order of things with your print ad, e.g. the pages, your pictures and images, and even your copy. If you don't think you have everything down pat, ask your printer to help you. They'll definitely know how to arrange your composition to get you a more effective marketing material.
Proofread more than once; and let someone else proofread for you.
Let's face it. After reading the same document over and over again, we tend to overlook some of the things that need to be edited in our print ad. To prevent having more errors in your final copy, let someone else look at your print material. In fact, let more than one person proofread for you. The more people to see your job, the more mistakes will be corrected.
Consider the texture and opacity of your paper.
When it feels cheap to touch, then you'd better change your paper choice because it'll just make you look amateurish and unprofessional. When you ask for a quote, go ask for a few samples of stock with different weights. You might miss out on a great deal especially when you just have to add a little extra and you'll already have a higher quality of paper.
Opacity on the other hand, if sufficient, can help you avoid those see-through images and text when your ad was help up to the light.