A few of the people who got here before me have (from what I can tell -- I haven't had time to read each post beyond a skim over, nor do I have time to) brought up a lot of the points I would've made, so I'm probably going to repeat a few things while offering some my own thoughts. I'm multitasking and need to keep this short anyway.
I suppose be warned in advance -- my posts are pretty long-winded, so read at your own discretion.
Some of the people here have suggested you get into the feeling of actually relating to your character -- honestly, this applies to pretty much all forms of role-playing, not just with romance. Of course, if you've never experienced deep feelings of romance before then it could make using this particular piece of advice difficult. Simply being sexually attracted to another person doesn't count as personally understanding either -- lust doesn't equal love, though naturally feelings of love will likely include sexual attraction; however, sexual attraction alone doesn't mean romance. Confusing a one night stand for romance is a fool's delusion. Since you've mentioned you're not talking about writing sexual scenes though, I probably don't need to go into this. It's just a common mistake for people to think smut by itself equals romance, which can bleed over into how people write 'romantic' scenes even if they don't include sexual content.
With that semi-diatribe out of the way, I'll get to my main points.
I'm in agreement that understanding the difficulties born from love (separation, loneliness, sorrow, loss, et cetera) will allow the quality of the romance to be improved -- there's a reason people say that 'absence makes the heart grow fonder'. I've been in a long-distance relationship with another member of this site for over five years now. They're in America; I'm in Australia. I can promise you that enduring this hardship has given our relationship worlds of strength that you will simply never see in a conventional couple. Getting the audience to see the struggles the two have to go through together will make their happy moments more endearing.
Out of everything I have to say in what I consider to be a post offering only a very limited amount of my thoughts on this subject, this is probably what I consider the most important -- you've discussed fearing that the writing will seem cheesy or forced. The best way to avoid it being 'forced' is to establish the characters' relationship well or don't bother at all, but it's the 'cheesy' part that I want to address specifically.
I'll be perfectly blunt with you -- I'm in disagreement with anyone who thinks you should avoid being sentimental when it comes to romance. As someone who is personally in a very deep and powerful relationship, I can tell you that a romance isn't realistic, compelling, or believable to me at all if it lacks very strong emotion. If you avoid being sentimental for fear of melodrama, I'll be more likely to read your story as people just being sexually attracted to each other and lacking real love, or if you're lucky I'll just think of it as an adolescent crush instead of a mature relationship. Long story short -- an absence of sentimentalism and melodrama will make the characters feel soulless to me. Real love is an incredibly powerful and overwhelming emotion. Anyone who suggests you don't portray it as such probably hasn't experienced love.
Also, this ties into another problem with criticisms that are directed at romantic pieces of writing. You've mentioned being afraid that you won't get the desired impact on people, but it's not possible to please everyone in the first place. Everything is entirely subjective when it comes to literature -- for every person who thinks that sentimentalism and melodrama are bad things, there's another person (such as myself) who thinks these things are required if you don't want the characters to feel like robots, regardless of whether the situation is romance or anything else. Ultimately, avoid hesitating to do something just because you think it might be 'cliché' -- nine out of ten times that's the most realistic option. Classical ideas - done correctly - are classics because they work; they are relatable.
Love - true, pure love - is a powerful, beautiful, compelling thing -- one of the greatest in this entire world. It might sound 'cliché' (not like I fucking care about idiots who toss out words like 'cliché' anyway) for me to say that, but it's true. Like was mentioned in the post prior to mine, there's nothing actually wrong with being cheesy because that's what love is. Criticisms directed at sentimental romantic stories often come from people who are superficial anyway, or people who hate love due to bitterness. At least, when not coming from someone who doesn't understand or relate to love in the first place.
On the other hand, it's very important to make sure you portray both sides of love, as my post and the previous one have emphasized -- nothing makes love more compelling than a little bit of realistic hardship or tragedy. I will point out - however - that this doesn't mean writing characters in a relationship who don't get along -- everyone has their bickering sure, but if the couple doesn't actually feel compatible then it'll just look like they're sticking together out of fear of being alone (which is, sadly, realistic, since many people do settle -- this doesn't make a good romance though).
Honestly, there's a lot of other things I could add to this thread as additional thoughts or advice, but I don't have the time. Perhaps I'll post again if no one else goes into them.
Edit: I noticed a typo, and I'm a perfectionist.