Read it out loud to yourself and then someone else too. The more you read something over and over again, it sometimes begins to all sound right or all sound wrong. A second opinion really helps.
A famous artist designed it for free, on condition we didn't mention his name, and hosted his gallery for 5 years.Â
Acrolinx. It's like your basic grammar check site on steroids. If you are serious about putting out quality content, I would check out that site.
I agree on reading the content for quality. It's also a good idea if your content is not in your language to have someone else proofread or edit the content as a separate project.
Get someone to read it out to you and you be the judge of it, if you like how it sounds then maybe it will pass the test otherwise have them write it all over again.
Have somebody else read it out loud. Every time they need to do a double-take or pause because they didn't understand something, you need to re-write it. Professional content NEVER has any flaws. Or, you can hire an editor to polish the article for you. Depending on how long your content is, it can get expensive though.