@Kishan Kashyap Check for plagiarism by diff. softwares available, that are paid also free of cost. Best is Copyscape.com If you want free, then go for smallseotools.com/plagiarism-checker/ or http://www.duplichecker.com/ (Y)
Tuiykkwr pointed you in the right direction to check if someone else has similar content as your, but at this day and age don't sweat it too much if you truly have been writing unique articles. Google won't hit you with a penalty because most of the things we say have already been said, somewhere on the internet, so don't sweat it too much.
To do it quickly in less than a minute. I randomly choose 3-4 sentences from an article and do a google search. I get a fair idea whether the article is genuine or copied. With some practice like this you will be able to tell which sentences you should check for. Particularly pick sentences that you like the most. CopyScape is no doubt the most used tool out there and it is reliable.