How to approach a client via social media, website or email?

Let's say, the web project is done, and I also have the presentation to my project.
Now, how should I explain my project to my potential customer?

Can I just write them on Facebook or email and tell them about our business type? Will it be a spam?

I would say "it depends". Spam is defined in Google as "Irrelevant or inappropriate messages sent on the Internet to a large number of recipients".

If I am on the receiving end of the conversation I don't care if it's only sent to me or 1,000,000 people. If I have no use for it, then it is a waste of my time, and I will despise you. I simply won't do business with you because you are rude, and don't respect me. I easily fire rude customers, with this I also fire rude or incompetent service providers.

So how do you get customers:

It sounds to me as if you lack an audience or network willing to pay for you and at the same time don't have money to market.

If this is the case, I would suggest that you network and become respected within a small network or society who will use your services.

In order to network effectively you would simply require a clear understanding of your service that you offer and be able to explain the problem that you solve in 30 seconds. Have business cards with you, and dish it out like candy on a schoolyard to anyone who is understands your service. INSTRUCT them to keep your card and give one to anyone who has the same problem. Then if you are serious about this, network. Do this at every opportunity. In pubs, on first dates, on last dates in interviews everywhere.

Building credibility in your network:
The best way to go about it is to build a slow but stable referral network. Rather network through people that you actually know, and let them know that you have a service worth X but are building up a reference list. With this you are willing to solve their problem for FREE.

It sounds crazy, but it works, but only if you do it the right way. And here is the secret, there is only ONE right way.

BARTER: Let them understand clearly that you have value in your product and that you are not scared charging a premium for it (show competence and confidence). Then let them know that you are building up credibility along with a referral network. Draft an agreement with them that you will do the work for free in exchange for honest and direct feedback + a testimonial that you can use. Let the contract state that this will be the payment for your service. Along with this put in a clause that they agree to refer three people to you in the future who will be paying clients if you live up to the SLA (Service Level Agreement) that you propose.

If you just do it for free, then they will disrespect and simply abuse you. But if they know that it's worth something, say $100 - $10 000, and that they are paying for this by simply giving you feedback and referrals, then they will psychologically feel that they have won and they will respect YOU as well as the service that you have provided them with.

DON'T MAKE A LOSS!
With this stated, don't be silly. Still charge them for input costs, but not for your value that you are adding in the process.

For example, if you are a chef, charge them for the electricity and the ingredients of the cake, not for your time or the secret recipe fee or for your skill in decorating.

REFERENCE: Personal life experience.
RESEARCH: Go research "Elevator Pitch". I can't remember where I originally got the idea, but it was in some personal development book from which I refined it into my own method.

CAUTION:
Do this only once per network line. In other words, never stack freebies, this creates an expectation that you work for free and have no real value.

In other words, if you did a freebie for one client and they refer someone else, don't do a freebie for them as well. Charge them and charge them GOOD! This will reinforce the idea that the first customer got value worth paying for. Phone the first client and let them know that this freebie was only for them, not for others. Tell him/her to not do this again but to send you paying clients. (When doing this, don't be rude, be direct and assertive.)

Good luck. I hope this helps in your context.

I don't despise people who send me unsolicited emails. If I don't want to read them, I hit delete. If they have been properly personalized and have been clearly written to me and not a "me living as a number on a lead list" I will respond with my lack of interest.

Or once in a while with interest. If the person who sent the email, or made the call, or dropped off the flyer made a compelling case that their product/resource/service/solution would benefit me.

If you remove from your sales and marketing tool box everything that has a potential of offending someone with unwanted communications -- then you will have an very light box indeed (and a very expensive one as well)

You don't need to send out huge spam mailings -- but you must identify your targets and reach out to them. Send them emails. On LinkedIn. From within the member area of association websites. If you use Facebook for business (look at their posts) then email them on Facebook. Go to their websites and send emails from the "contact us" page. Ask your contacts who they can refer you to and send them letters too. Pick up the phone and call them. Stop by their office and leave a hand written note.

You are now entering the space where people will hit delete on their key board, find a reason to walk away from you at the mixer, hang up the phone quickly, and cancel a meeting. It is a space called sales.

And that is just the way it is. It will make you a little tougher, a little smarter, a little more focused. It may also make you a little more tolerant when a sales person reaches out to you! :)

Open up a dialogue with them, not necessarily selling them. It's non threatening, you'll learn from them, and you may pick them up as a customer or they may recommend someone as a customer...

First email: "Hey, would you mind taking a look at this project I'm working on? With your background as _ ___ , I think you'd offer valuable feedback. Thanks,..."

Second email: "Hey, you're likely busy, but would you mind taking a look at this project when you have a moment? I think you'd offer valuable feedback, because..."

Response: "Sure, just let me know what kind of feedback you are looking for."

Response back: "Just a reaction to the idea, and maybe some thoughts on who would be some potential first customers. Thanks,..."