PP - we've had similiar issues about crying etc. If you ask her what it is that upsets her will she tell you? I had some fab suggestions from BB'ers just after school started. DD1's issue is leaving me and not wanting to go to OSHC on the days I work.
We found getting used to the daily routine helped - so me running through what to expect each day and having something to focus on in the morning - so Monday is assembly, Tues library, Wed...... I also bribe her with a lunch order once a week and we had a star chart to get a Build a bear at the end of term. She was allowed to wobble a bit but needed to be composed when she went into class. We also had a clear cut routine to say goodbye - so I try to get ready with heaps of time so we aren't rushed out the door as this makes things worse (not always possible). To help this we lay out the next days clothes the night before and pack her school bag with the necessary bits. I also as much of her lunch as possible and keep it in the fridge. Sounds OTT but I really notice when things are rushed that she gets more wound up. On the days I am home we walk and chat, counting the crossings, house numbers etc and this also seems to help.
I think the biggest thing that has made a difference is that I have organised a heap of play dates too - she didn't know anyone and we have really made a massive effort to get a social network going for both her and us, I have felt like a bit of a stalker and it really has been quite a big effort. We have made some lovely friends as a result and are now very deeply entrenched in school life - I also found lots of other people who were in the same boat. Most people are just so pleased that their kids have friends as well!!! Good luck - it is such a worry but you will get through it. We still have bad days but that's ok. xxx