We had two daycare situations: a nanny-type and preschool-type. The were both fantastic for different reasons. We did the nanny-type until 3.5, then overlapped with preschool... and she still sees our son one afternoon a week, because she's amazing and we love her influence.
The two biggest pieces of advice I can give regarding leaving are patterned goodbyes and nonchalance... they tie together because the single best thing you can do, is with every ounce of your being, be happy/normal/relaxed/at ease.
The reason?
It's usually a lot harder for the parents to transition than the children.
Babies and children take their cues from us. They watch us (or if we're holding them feel us)... if we're nervous, upset, sad, etc... they see a bad situation coming on & react badly to it. After all, if Mum! The guardian of all that is right in the world, is upset there must be something REALLY scary about to happen.
If you've ever had the misfortune of having a miserable day, being stressed out of your mind... with the baby crying... and then not five minutes after someone else takes them (dad, nana, friend, etc.) the baby is not only quiet but asleep and you're torn between relief and mortal jealousy... you know exactly what I mean. Cycles of negative emotion feed back and forth inciting stronger and strong reactions. Nothing mystical about it, just a natural behavior response.
This hold true for years and years. If you're anxious and upset, your little one will be, too. So if you're dropping off... and nervous... fake it. I can't count the number of times I've seen crying parents and crying kids... and then the parents saying that their child HATES "x". Sigh. USUALLY, as soon as the distraught parent has been gone for a few minutes the child takes the happy cues from the other people around them and has a blast. Distraught parent picks up, and the child breaks down right with them.
Poor things, all around. Such a vicious cycle. So when you find a person or place that you TRUST after vetting... go with your gut and TRUST them.
Patterned goodbyes are easy... you already do them every time you lay down for a nap, or bedtime. I don't know about you, but I had to have someone else point out that it makes strong attachments sooooo much easier in regards to going to and fro. Mummy does her "thing", she goes, she comes back. Imprinted and driven home into a faith through repetition. Mummy always comes back.
I learned patterned goodbyes from my mum and early daycare (having a ritual; ours was hugs, kisses, and waving with HUGE smiles all the way to the car, with his little arm being waved until I was out of sight). Routines for leaving (like bedtimes, and other transitions) make those transitions easier.
Good Luck