I have a flower garden area in front of my condo that I moved into this summer, and this is the first time I've really had to do any landscaping.

My fiance's mother and I both planted different plants throughout the summer - some perrenials, some annuals. My question is... if they're not perrenials, do I have to do anything (pull them out, etc.) to prepare the ground for next year, or do I just let them die and decompose on their own?

We also had a lot of weeds this year as the previous owners neglected the space. I dug them up constantly, and used some RoundUp towards the end of the summer. Will they come back next year, and how can I prevent them with minimal maintenance and no damage to the 'real' plants?