In my tireless efforts to inform and entertain you, I find myself wrangling a lot of pictures for posts here on CoM. And now that many people are coming at us from Retina-screened devices, we try to use big pictures whenever we can. But how big is a picture?

Clicking the image and tapping the spacebar will give you a preview, but it won’t give you the image’s pixel dimensions. Not unless you install QuickLook plugin qlImageSize.

There are many files that help make your system usable, but they can build up over time. System logs, for example, keep track of usage, errors, and services running on your Mac, but unless you look at these often via an app like Console, you’ll probably not need a ton of log files taking up space on your Mac, especially if you have one with a low-volume SSD.

QuickLook cache files make your Mac feel zippy when you hit the spacebar to preview files in the Finder or Open/Save dialogs. If you can stand a bit of a wait to do this, deleting these files can save you some space as well.

Put together, you might save a decent amount of space on your hard drive, so give it a shot. Here’s how.

I’ve been doing this quite a bit lately, and didn’t even realize it was a new thing until I did it in front of a friend the other day, and she said, “Woah! I didn’t know you could do that!” So, forgive me if you already know this, but give it a shot if you didn’t.

Ever try and browse through the default Open File window? The icons can be super small, especially in List View. If your eyes aren’t up to the task of figuring out just which Picture.jpg you’re looking to upload to Facebook, then give Quicklook a try.

Quicklook is Mac OS X’s way of letting you see any file up close with just a tap of the spacebar. When you’re in the finder, for example, and you click on a photo, you can hit the spacebar and see the photo large and up close, making it easier to figure out which images to toss, and which to save. You can do the same with any supported text file, like an rtf, doc, or pdf file to see what’s in it at a glance.

But what if you want to copy a quick bit of text to paste somewhere, like an email? Instead of opening the file, waiting for the associated app to load, and then copying the bit of text, give this trick a shot.

Apple’s presentation software Keynote is, in my opinion, a fantastic application for making presentations on your Mac. It’s easy to use, presents a unified metaphor for designing slideshow presentations, and makes using rich media a very simple process. Unfortunately, not everyone who uses a Mac will have Keynote, as it seems that Office is the de-facto standard in many businesses and computers.

Fear not, however, as viewing Keynote files on a Mac is super easy, even if you don’t have the Keynote app itself, which is also an affordable and very worthwhile $10 in the Mac App Store. Here are three ways to do just that.

Ever need a quick look at a bunch of pictures in one folder all at once? QuickLook is all well and good, but it’s a slow-going one-photo-at-a-time. You could use iPhoto, but for a quick check of a folder full of images, that’s a bit labor intensive. For our money, today’s tip may be the fastest way to see all those photos at once.

Back in Tip #27, we showed you how to use QuickLook, an extremely handy way of previewing all sorts of different files on your Mac.

QuickLook is particularly handy for checking out image files, especially when you have a folder’s worth, all with identical generic icons rather than thumbnail icons, and you’re not sure exactly which one you want.

It also has a hidden secret feature: you can zoom in to images while in QuickLook mode. Here’s how.