So you've dropped your older iPad 1/2/3, Mini 1 etc. and now it has no display, or the display is grey, but it is not cracked. What do you do?? Well, first I would recommend you go Apple's website to check if it covered under warranty https://checkcoverage.apple.com and entering your serial number found on the back of the unit below the text "iPad". This will tell you if your iPad is covered under Apple's own warranty, and if it is, you should take it to the Apple store and they will be able to help you unless there is obvious physical damage such as a crack on the screen or dents on the sides.
What if your iPad is just too old and Apple won't touch it, and you don't want to spend $100+ getting it repaired? This unorthodox method might get you back up and running until you're able to buy a new iPad or tablet.
WARNING: PLEASE ATTEMPT THIS AT YOUR OWN RISK, WE ARE NOT RESPONSIBLE FOR ANY DAMAGES OR LOSS OF DATA. ONLY DO THIS AS A LAST RESORT
Step 1: First try holding the power and home button at the same time for around 15 seconds and see if that fixes the issue.
Step 2: Make sure you don't have any important files, photos, or documents on your device, if you do, please take it to a professional to get your data off.
Step 3: Wrap the iPad generously in bubble wrap or some kind of fabric, so it has a good buffer in front of the screen, and make sure it is secure with either tape or something similar.
Step 4: Drop the package containing the iPad from about chest height onto the floor a couple of times. That's right, your fighting fire with fire!
Now check if the screen is working again, there's a chance it is, albeit probably temporarily. What most likely happened to the iPad originally to cause it to have no display or a grey screen, is when it dropped the first time, the connector going to logic board from the display came loose, or an electrical component on the logic board became a little bit loose. Either way, it will probably happen again, so it might be a good idea to start saving for a new tablet.