By default, most of us use Grammarly these days, it's not the 100% perfect tool for finding out your mistakes, but still, it's pretty awesome for people who type fast and lazy enough not to proofread it later (like me, exactly). They have a free version, which has basic features and it's pretty good. But, they also have a 'premium' version which is much better than the free version + they also have "Plagiarism Checker", which is very very important to me since I get plenty of guest articles every week.
Here is a small tip/trick to get a Grammarly Premium account for free* for a week, you don't need any access codes for this or any EDU trick.
1. Install Grammarly browser (Safari, Chrome or Firefox) extension if you haven't already.
2. Log in with your Grammarly free (not premium if you already have one!) account.
3. Go to any website which supports Grammarly - Facebook, Twitter, etc.. and right-click the Grammarly browser extension icon. You'll get something like this (Google Chrome):
Click on "Invite Friends" button at the bottom. You'll be redirected to a page like this:
Here you can invite your friends by entering your email address, and you'll get your exclusive referral link as well. The best part here is, you'll also get a free week of Premium access when your friend/visitor signs up and installs their browser extension. Both you and your friend gets it! You can share this link with your friends on Facebook or Twitter, they'll get a page like this:
Now, they just have to click on the "Get Grammarly" button at the top to get their free Grammarly Premium account which will be valid for a week. This one week is just for a single friend referral, if you have more cool friends who are generous to register via your link, then you can use this Grammarly premium for more weeks.
But again, if you don't have more awesome friends, then self-help is the best help, enter your other email addresses and grab this, I won't suggest this in the long-run, but still...
Do let me know if you have any other queries, I'm using Grammarly Premium for several months and it's very helpful for me, let it be blogging or social media updates.