There's a reason why the "freemium" model (basic services for free, additional features after premium upgrade) has become so popular: users don't have to take a big leap of faith but first can see if the service can add value to them. Also, after you provided some value, users are also more willing to pay for extra services as they deem it fair (you provided value to them, now it's their turn). First give, then take.
In a similar vein: Offer your entire service 30 days for free. That way your users get used to it, and don't want to miss it anymore by day 30. Give them the full 30 days, as habits (i.e. getting used to something) usually takes at least 30 days.
Once you did so, place the statement that you offer things for FREE very vivdly. The word "free" still does magic in the world of marketing.
With an affiliate - or referral - marketing program you can incentivize people to spread the word for you: everytime they refer a client who makes a purchase, they get a share of the revenues.
Read more about affiliate marketing on Wikipedia.
Small, nifty & free tools can be a great way to generate interest & traffic which you can then leverage for your main (paid) product.
For example, Freckle, a paid time-tracking app, launched a cool tool which easily allows you to check the current time in any location in the world. It got press coverage from several high-profile news sites despite (or maybe because) being a very simple tool.
Another example for a free tool is HowMuchToMakeAnApp, a tool which tells visitors how much they can expect it will cost to create a mobile app. Users get taken step by step through the process and asked which features they want in the app, which will define the final price. And, incidentally, at the end users get asked if they need somebody to build the app for them...
Maybe this sounds lame, but if you find a business which is complementary to what you're doing, and maybe struggling (so that it's not so expensive) then acquiring another business can be great for growth.
For example, think about businesses in your niche which have a lot of users, but are struggling to make money. If you have the revenue-side figured out, then an aquisition can be beneficial for both parties.
Check out this case study.
Another way to look at competition: it's not a competition of products, but a competition of business models.
If you're in the paid advertising space (and you will be eventually, if your company is going to be successful) then you will compete with respect to how much you can pay to advertise. For example, on Google the company's ads will show on top who are capable to pay the most for them.
Therefore, you need to ensure that the value you get from advertising (e.g. a user clicking on your Google ad) is higher than for your competitor. So think about how to maximize the life-time value of every customer - if it's more than your competitor's then you will dominate the paid advertising space.
Re-targeting (or re-marketing) means that you advertise to people who already know you. For example, a user comes to your site, puts a product into a shopping cart, but never makes the purchase. You then show him ads on other websites (e.g. Facebook), telling the user to come back to your site and complete the purchase.
Re-targeting is very effective because the users already know you, i.e. you are already familiar to them.
There are different applications you can use re-targeting for, have a look at this introduction:
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