oh goodness, three daughters here, and each very different in their experiences, and how I approached 'the talk' with them
~What sort of approach works best? Who do you think should start the conversation off?you or your DD?
This one might have been the easiest, and actually, probably the most similar with each. I have never ever had privacy in the bathroom. We had to hide the key when DD2 locked herself in and we had to break in, and then said key, in its 'safe place', disappeared for YEARS. Therefore, they saw me having periods, using protection etc, and asked in the way small children do. I told them what was age appropriate each time, but they grew up always really knowing.
~ How does your DD feel about discussing periods with you?
DD1, very open.
DD2....I would not know when she is on, or even if she is in pain. She does tend to sail through her tho with nary an ache or niggle 
DD3....very very open, but she was the youngest starting her periods, and has hell with them every month. Lots of pain, lots of flooding, lots of hormones. She suffers, and so we talk.
~ What do you think is of interest or concern to your daughter at this time?
The greatest fear from each during their period is that other people can tell, or see evidence.
~ What about protection? How do you and your DD decide which option to go for - does this change as they get more used to having their period or get older?
When each of them started I bought some of everything, so they could work out what each of them prefer. Pretty much tho they have all settled on the same brands I use and trust.
~ If your DD suffers with menstrual cramps how do you manage this? Are there any practical things you can do to help your DD if you suspect she is about to start having her periods?
I have in medicines aimed at helping cramps, plus hot water bottles, and tell them warm baths help.
Nothing helps more however than sympathy and a hug.
~ Finally, mood swings are commonplace during puberty to you have any tips or concerns you can share? - (or should we not even go there?!)
Oh god, mood swings. Lets just say that with three girls, and me, all suffering and arguing......my poor husband and two sons hate that one week of the month when we all turn evil 
~ What tips or advice would you share with other parents about puberty and periods?
Just go with the flow (not a meant as a pun
). If they ask questions, answer them. Dont hide it and don;t be ashamed of what is, essentially, a normal part of being female, and what will be part of their lives for probably 40 years.
And have lots of hugs ready.
And a place to hide...I hide in the car.
oh, and wine. You need a lot of wine to cope with teenage hormones.