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What Amadeus says about body language is true, but it can be hard to convey in prose. It is the  kind of thing you can rely on actors to do well in film, if that is the medium (as the 90 second time limit suggests), though that really doesn't leave you much to write. 

In prose (and in film as well, if you don't want to leave it entirely in the hands of the actors), try larger gestures. The marriage proposal, for instance, is a formalized set of gestures (down on one knee, the presentation of the ring, the hands clasped in surprise, followed by the finger extended to receive the ring, the rise, the kiss) that is highly recognizable without the words. 

There are many other ceremonies of affection as well, such as the sharing of an umbrella, the presentation of a flower, shopping together (especially for furniture, or a puppy).

Friendship has its ceremonies of affection as well, thought they are different from those of romance. Going to a game together. Sharing a drink. Helping fix a tire. Looking after each other's kids. Providing a shoulder to cry on. String a few of these ceremonies of affections together and you can tell a whole story by implication. 

Note that these ceremonies of affection actually speak more powerfully than words. It is harder to lie with actions than with words. If you want to know if someone loves you, which is the stronger indication? That they say they love you, or if they act as if they love you? Similarly in a drama, the ceremonies of affection speak louder than words.