There are several websites offering money to undergo online surveys, carry out online searches, and write reviews on products. To get the credit, one needs to disclose certain information to them including one's banking details. This is why you should use this route with utmost care. Some of them may even ask you to register with them before working on projects. The most important watch out in such projects is to stay away from websites offering money that appears too good to be true. Be careful while evaluating the reputation of the website as many of them could be a scam. Most sites promote businesses showing copies of cheque payments which may have been given to the middlemen only.
For those with a large Twitter following, you can make money from your Tweets alone with Sponsored Tweets. You could be paid for sharing a business’s information, recommending restaurants or hotels, or tweeting pictures of you using or wearing products. As with all sponsored posts on social media, businesses will only be prepared to pay you to Tweet if you have a large following that you can influence. So work hard on building up a loyal fan base.
Mechanical Turk: Amazon's Mechanical Turk is a resource for doing human-intelligence tasks, or as the site commonly refers to them, HITs. You get paid a very small fee for any given HIT and you'll need a good deal of volume to make a substantial amount of money. But it is a resource you can use in your spare time to generate a small income online.
If you have a good idea for an app, and the skills to create it, then producing your own premium app can be profitable. However, with so many free apps available, it may be hard to convince people to pay. If you want to go down the premium app route, consider having a basic free version to encourage people to download the app in the first place. You can then provide the option of upgrading to a premium plan once users realize how useful the app is.