Hey Epiphora has a good list of tips that you can find here
. There's also a good list here
on Insatiable Desire.
Generally, just include as much information as possible. Answer any questions you personally had about the toy before you bought it and any questions you think anyone else may have. Discuss anything interesting you discovered while using it that couldn't be determined by looking at the product page. Discuss basic stats on the toy and care instructions. Make sure you talk about how it worked for you personally, otherwise your review is just a really long product description. Make sure you have accurate information.
I see you have a mentor already (and a great one at that!). If you get to writing and find yourself at a loss for where to go, that's what she's there for! Either message her or send her what you have with a little comment that says you were unsure of where to go from there.