Keeping the conversation going

So i recently moved to a new neighborhood and they have this great big park where i walk with my dog, multiple times a day. I also come across plenty of women and i always great them, i am a friendly guy, haha. So last sunday i was sitting on the bench and my dog was sniffing around and this rather nice looking young lady walks past me and stops and lets her dog and my dog become acquainted with eachother and we started talking about the dogs..you know, the usual...''nice dog, how old is he/she, name?'' and that was about it. She was really friendly and it was a nice talk but it could have been so much more. I've always sucked at this and i hope i can improve with this aspect of life. No problem starting a conversation with a lady but keeping the conversation going is what i am bad at, soon i run out of things to talk and if she does too...that's about it. My problem is that afterwards i start to think about it a little and all these ideas for conversation topics come to mind...things like...''hey i recently moved here, so i am new here. What's your opinion on this neighborhood? Nice weather huh? This is a great park isn't it?'' especially the first subject in my opinion is most likely to spark a longer conversation but i hate it that i always think of these things when the person has already left.

I could use some advice on how to improve on this or you know, interesting subjects to talk about. And it won't necessarily be only for this lady but just women in general.