It can be a lengthy, emotional letter, or just a quick "I love you!" jotted down on a Post-It note. For extra points, write it by hand on pretty stationary.

You can go all retro and have a milkshake with two straws. Sharing the same glass of wine can also be pretty sweet.

Open the door to the car or restaurant for your SO. It's a tiny gesture that conveys a lot of care.

It doesn't matter how well either of you dance. Just hold your partner and sway.

It's more than just a sweet gesture. "When the fingers are interlaced and someone is holding your hand, they’re stimulating pressure receptors [that trigger] what’s called vagal activity," as Dr. Tiffany Field, director of the Touch Research Institute (TRI) at the University of Miami/Miller School of Medicine, told HuffPost. "When there’s pressure in the touch, the heart rate goes down, the blood pressure goes down, and you’re put in a relaxed state. When people interlace their fingers, they get more pressure stimulation than the regular way of holding hands.” Simply holding hands can affect both of you in a deep and positive way.

Offer your SO the last bite of a tasty dessert and feed it to them. It's a super intimate and kind gesture.

Whether you've been together for a few days or a few years, keep the flirting going. Making flirting and playfulness a part of your relationship will help keep things fun over time, as intimacy expert Dr. Gayle Friend explained in her blog.

It's a sweet move, even if you're a little self-conscious about your singing voice. The song can be as silly or meaningful as you like.

Food is love. Surprise your partner by cooking (or attempting to cook) their favorite dish.

You can't go wrong with flowers. They've been a classic romantic gift since forever.

Even if you're just heating up a frozen dinner, candles add romance to any meal. Fire up the tea candles as often as possible.

Those goofy names you call each other are actually important for bonding. "I think it’s a really human, natural behavior to take language and shape it for our own purposes," said Carol J. Bruess, director of family studies at the University of St. Thomas, in Scientific American. "I think that’s how nicknames evolve." Calling one another "Sweet-Sweet" or whatever else is just a quick way of showing affection.

Even if you've said it a thousand times before, compliment your partner's gorgeous eyes or great sense of humor. Everyone likes to feel appreciated.

Don't just kiss. Kiss. Do a dip and kiss your partner Old Hollywood style, as noted in Best Life. It's perfectly romantic.

It doesn't have to be anything expensive or fussy (unless that's what you want). But schedule time for a proper date from time to time, whether it's dinner and a movie or meeting up for drinks after work.

Take advantage of that randomly perfect Sunday afternoon. When the weather is nice, pack a lunch and eat it at your leisure in a park. It's the simplest date ever, but there's something very romantic about enjoying your partner's company in this way.

If your SO is freezing, offer your coat (or at least a warm hug). It's a kind and classic gesture.

So enjoying a long walk on the beach may be one the most cliche romantic moves ever. But it exists for a reason. Hold hands and take a stroll around your neighborhood, a local hiking trail, or the nearest beach.

Make a playlist just for your partner. The songs can be as sexy, sweet, or silly as you like.

Massages are free and so soothing. Even a gentle shoulder rub can bring so much relief.

Say it often and with sincerity. Nobody can hear these words too much.