Good posture is essential (strap or strapless) you need to be able to glide your fretting hand up and down the fingerboard with ease. If you have to spend time worrying about holding the ukulele it will be an unwanted distraction.
Concentrate (always, every time you play) on hitting the note directly behind the fret wire and trying to extract every last bit of sustain out of it. Timing is a big part of sustaining notes, you need to hold the note cleanly and not rush to get to the next note. Practicing songs very slowly, note by note will help develop more accurate fretting and cleaner, clearer notes. I do this regularly with instrumental songs that I've played for years, just to make sure I'm on track and not developing bad habits. Creeping variance is the enemy, it's very easy to drift away from a good technique.
Practicing good technique is another way to enjoy the ukulele, it's no big deal, it even makes it more enjoyable, if that's possible!
I forgot to mention that a lighter touch comes from more strength. Developing strength in your fretting hand is essential, the more strength you have, the less effort is required. It sounds crazy but that's how it works.