Say, you have built an awesome cloud-service. Collaboration tool, some kind of analytics service or a fancy group chat. Chances are that you are going to have to offer a Trial.
Typical, conventional, boring, "me-too" way of doing it is to offer a short term free access. 14 days or a month is what you see most of the time.
This is fine if you just want to demonstrate your app/service. You could even collect credit card details right away and then hope they wouldn't notice the charges (dirty trick of the trade).
If, however, you want to attract lots of Trial users, retain them for years and make them buy your services, well... do what the big boys do!
You need to captivate them. Start with understanding what the word "captivate" actually means. You can
find google definition yourself, but I suggest paying special attention to the main synonyms:
Fascinate. Show what you've got and don't talk about money at all. Like it doesn't matter. Bring all your guns. All the features. Promise salvation. Make them want to lick your buttons. Say "thank you" and "please" all the time. Say "magical" and "unique" and "best" and "simple" and "easy" and "unlimited". Say "no obligation". Focus on attraction.
Bewitch. Now that you've got them to sign up and spend some time with your product, start casting spells. At this stage your focus is on retention. Good method is to make them invest some time into setting things up. Make them feel at home. Walk them though customisation process. Remind them to create profiles, upload media or docs, start chatting, integrate with other tools they might be using. Get them to publish their posts or send invitations. Entice them to recommend or just brag about their choice. Make it hard for them to leave. Throw in some extra suprise-features and referral benefits.
Charm. Offer a "Premium" option. Don't say that their option is crap (yet). Just suggest that Premium option would turn them into premium humans instantly. Say "instant success", "breakthrough performance", "immediate return", "enterpise class" (whatever that means), "advanced", "secure", "sexy" (ok, don't say sexy, but allude to it). Focus on glamour. We all know they don't need your Premium option, so don't waste time talking about practicality. Talk about glitter.
Subdue. And when you're almost out of VC or piggybank money, start subtly slowing free things down. Don't just cut them off. Empathically recommend upgrades to "avoid interruptions", "take advantage of avant-garde technology", "maintain growth" or "access all features". Now, offer a Trial! "No-obligation", and all. Just don't forget to inject words like "you can downgrade back". Plant a seed that their tier is a "downgrade" and that using it is like going "back". It's not exactly crap, but it's definitely not sexy. Next up, you can start taking away the old gifts - remove surprise-features, put upgrades to slow-cycle, depreciate a few 3rd-party integrations. Finally, start calling free version a "legacy" and announce that next update won't support it fully. Some things "may" remain, but it's better to upgrade to a (currently on special) Premium version. Focus on suppression.
There is one caveat. "Captivate" method requires three things: money (to cover costs during the first 3 stages), confidence in your product and optimised site logistics. All those pitches, up-selling, account registration and communication routines must work flawlessly.
To illustrate the method, we can just glance at what Google did with their Google Apps suite. Launched in 2006 as a completely free service, Google Apps was initially regarded as a "basic" alternative to proper productivity tools. Gradually, drawing from the strength of Gmail the Apps attracted millions of businesses, web-masters, bloggers and other relatively tech-savvy folk.
Google Apps kept improving, adding social features, new apps, tie-ins with other services, increasing storage allowance and still not even a peep about paying for it. It even allowed combining emails forwarding as aliases from multiple domains, all sending via Gmail SMTP. It went on and on. If you are doing any kind of business and/or collaboration online, you're using Google Apps. It's has become de-facto standard. A commodity.
Later they've launched Premier Edition or Apps for Business. More storage, better features, safer, faster, yada, yada.
In 2011 free version becomes available only for organisations with under 10 users and in 2012 free version is no longer open for new customers.
There is no uproar or hunger-strikes. We get it. We should pay for good stuff. And the smarty-pants techies could add more domains to their existing "legacy" accounts, feeling jammy about having a pay-for goodies for free.
And sure enough, in 2014 Google's tyrannic plot starts to unravel. Secondary domains are not supported and email forwarding as alias doesn't work with Gmail SMTP. For most power-users this means forced upgrade. $5/month doesn't seem like much. Well, it's not exactly cheap when you add up a team of, say, a hundred, over 12 months. That's a noticeable $6000/year, but hey... it's Google Apps, we have to have them. All our emails, shared files, chat transcripts, bunch of photos, calendars and business photos are there.