Hanging art not at all like a pro
The internet is bursting at the seams of how to hang art like a pro - masking this, measuring that, making a whole damn paper mock up of your wall...which is great and all, but perhaps also goes a way to explaining why almost all of us have prints and pieces in envelopes or frames, stacked in a corner. That the fear of doing a bit of crap hanging job is what is hanging over us, when really we just need to get over it and get that art hanging over us instead.
Things to get over
Whether you're going to use little picture hanging nails, or sticky hooks the main thing to remember is that the potential mark on your wall is TINY. It's like a freckle on your face versus a forehead tattoo and yet we act like we're doing this huge momentous, irreversible thing. We're really not.
Second thing worth remembering is that if you hang something on the wall and it's not in quite the right place or you need some other things to finish the look you won't actually have hoards of judgemental art critics lined up outside your window (unless maybe you live next door to some super bitchy art critics club with a strict bouncer on the door).
Third thing, which actually applies to everything in life is "Done is better than perfect". Because what joy do you get out of that beautiful print you treated to yourself if it's stored in a cardboard tube at the back of the cupboard? You would get more out of it if you just blu tacked it to the back of the bathroom door (I'm not suggesting that but also, back of the door art is perfectly ok). It's like saving that amazing cheese for something special, by which time it's gone off when you really should have just scoffed the lot in front of the tele and had the BEST night.
And, third thing side note, this applies to framing too. Professional framing is beautiful but can be pricey, especially if you've got a bunch of stuff to frame. Stick things in ready made frames with a promise to yourself to have reframed when you can, get custom mats cut to make non standard sized things fit in standard off-the-shelf frames.
Things to do
Ok, so let's assume you're no longer fearful of messing this up, you've got your art and you want it up on the wall TODAY. What do you need? A box of picture hooks from the hardware store, a hammer, and some picture wire (probably came with the hooks), a bit of confidence (but really only a little bit). Doing a whole "how to" would completely contradict everything I've said about just getting over it and doing it, so I'm not going to do that. Just a few little tips to get you started (like Dad holding on to the back of your bike and then letting go when you don't realise but far less dramatic)...
Start at your sightline. There seems to be the instinct to put art quite high up on walls, perhaps people think that they're going to sit on the sofa and then slam their head back in to the wall. This doesn't actually happen. (if it does, consult your GP). Instead place art right in your sightline, remembering that you are in fact not a giraffe but merely a human. Next time you go to a gallery, appraise the height of their hanging, it's almost always lower than you would guess. If you are stacking art, or doing a gallery wall - centre it around your sight line, don't start with the lowest at your sight line.
String your pictures with wire. Lots of cheap frames come with a little metal hook on them, which seems super convenient until you realise they are NEVER centred which means your picture will never be straight. Wire means you can wiggle stuff around.
Not quite straight? Stick some power tac or blu tac in the bottom corners to hold the frame where you want it to stay.
Not-planning a gallery wall - this is my favourite, I can almost hear the gasps of horror from pinterest. If you've got a bunch of stuff you want to hang together but the planning part of it just makes your head hurt, just quit planning and start doing. Start near the middle with your favourite bigger piece and then just work out from there. It's OK to move things (remember how tiny those holes in the wall are) or find something to plug a gap (postcards or cards in small frames are the unplanned gallery wall's best friend.
Insistent on going for the grid - you can't really avoid using a measuring tape for this look, but you can still 100% DIY it without dying. A tip is using the 3M velcro strips (not an ad) so that you can make incremental adjustments super easily to make it look perfect! Also, cut a right angle guide from cardboard for spacing each frame next to each other.
So, let's hang out! Trust yourself, don't over think it, doooo it.