I think the best time to visit Beijing is spring ,for the weather of that time is very fine,neither too hot nor too cold. The warm wind will make you fell happy.
Many people visit Beijing for it's beautiful scenery and cultural inheritance.
If you want to have a enjoyable journey, I suggest you to pay a visit to the Great Wall, the Summer Palace, the Olympic Park and many other place.
When you feel tired after one day's journey ,you can taste the Zha Jiang Mian ,a kind of traditional food in Beijing.
There are many other things you can do in Beijing, as shopping in the big shopping mall, visiting the different kinds park ,visit the Si He Yuan.
Beijing is a major transportation hub, with dozens of railways, roads and motorways passing through the city. I expect you to visit Beijing。