When presented with any opportunities, make sure to give at least 12 hours before making the decision to take it.
A common problem for new freelancers is to undercharge their service. If you find yourself in such situation, don't be afraid to raise it radically.
It may seem like a competitive edge to set your price low, but your clients would also have lower expectations of you. This means taking on projects that require less talents, and therefore a bigger pool of competitors. Plus, if you are charging low prices and barely scraping by, you would end up having to spend more time on more projects, and less on developing your skills & being happy. Higher prices, on the other hand, motivates the client to give you challenging projects, and you to do a good job on them, growing your skills in the process.
When negotiating, use the price anchoring technique, or in other words: say the price first. This sets the "anchor" of what the final price would be.
when HR asks you how much you want too early on, don't give a number right away; give them a document explaining why you are worth that price.