I recently shattered my iPhone 4s screen. The phone still worked but my beautiful retina display was turned to a splinted mess. I decided to try fixing it myself. My final money out was about $60 which is much cheaper than the $200 I've read Apple will charge. I did have a few issues along the way and here are my 10 biggest tips that would have save me much mental anguish.
Red 4s Screen
Dark Blud 4s Screen
White 4s Screen
Black 4s Screen
Back Up your Phone
In the unlikely event you can't fix your phone you don't want to lose your stuff
Make sure your tools fit
you will need :
TS1 Pentalobe Screw driver
and a #0000 Phillips head Screw Drive
Most replacement screens come with a set of tools - but they suck - I broke the philips that came with my screen and neither of the pentalobes fit.
A magnetic tip is a wise decision.
Take note of your screws.
There are 20 screws an only 12 of them are the same, but they all look similar. The screws aren't all interchangable so if you put a screw in the wrong hole it may get stuck.
Set aside 1-2hours.
If you get interrupted you risk losing your place and your screws. They are little and difficult to work with. I spent about 6 hours on my repair due to not taking note of my screws. My eagerness to fix my phone led to many mistakes that could have been avoided.
Watch a disassembly video first.
I watched 1 about 10 times. Also some good documentation like this PDF has pictures and will also help you out.
The battery, screen, vibrator and cables all have double sided tape on them. The video I watched didn't explain this, so I was a caught off guard by how hard I had to pull.
Limit power tool use.
I'd suggest not using them at all but whoever assembled my phone had he-man strength. I just couldn't get the right leverage without the use of a power drill. Be aware that it is very possible to strip screws if you aren't careful.
Don't tighten your screws as tight as they were.
You may have to go back in to reattach a cable or something and if you wore your screws too much taking them out and then putting them in you risk stripping them.
If you strip a screw - I'm so sorry for you.
I had to Dremel a slot in one of the shield screws because I had mangled it so badly. I'm sure it was the wrong screw in the wrong hole, but I couldn't get it out with a philips anymore. I had to dremel a slot so a flat head would go in it. I had to get it out because I had a loose power cable and I couldn't turn my device on. Luckily the dremel could fit. If my screw had been anywhere else I'd have been SOL and would have probably had to cut the screw off. Be careful and take note of your screws
Take a break if something goes wrong
If it weren't for screws this would be a 10 min job. If something goes wrong take a break. Nothing raises your blood pressure like a $600 phone in pieces and you can't do anything about it. Take a break.