4) It is not hot! Don't think that because it is in the "tropics" it will be warm. Bogota is the 3rd highest modern city in the Americas (after La Paz and Lima), and because it is in the Andes, it will be cold; think of it as an eternal spring/autumn. Annual average temperature during the daytime ranges from 58º to 68º F, but at night it can drop as low as in the low 30's. Bring yourself a nice leather jacket or a thick coat; people also use scarves and even gloves from time to time (usually late at night). On freaky days we do get up in the low 70's all thanks to global warming (thank you humankind!).
It rains a lot! Bring an umbrella. We also have a windy season and if I recall well, it's usually in August and you will see a lot of kytes up in the air (competitions and festivals to celebrate the windy season also occur around this time).
5) December: I think it's the best month to visit because you see true Colombian traditions come afloat thanks to the holiday season. Being a country of mostly Roman Catholics, you will see that the whole month of December is dedicated to Christmas, not because of the shopping, but because of the nativity scenes erected throughout the city (from churches and cathedrals, to schools, parks, homes, and even shopping centers!), the city is filled with lights all month long representing the spirit of the season. People make it a point to drive around to search out these nativity scenes and light displays. Another thing to keep in mind is that there is serious and heavy partying going on during Christmas and New Years. Lots of great food, and plenty of alcohol to be had (please don't drink and drive). There are also other traditions like El Dia de Los Inocentes (I can't recall if it's on the 28th of December or November, but everyone tries to prank everyone else; even in the newscasts! It's all fun and games and it is to honor the innocent souls of children and other kind-hearted spirits. A New Year's tradition in some homes and neighborhoods is the Año Viejo (The Old Year Doll): people make a life-sized doll by filling old clothes with newspaper and fireworks and they call "him" Old Year. At midnight on New Years Eve, everyone gathers on the block and hand this doll and light him up (to burn all those bad things from last year away and start with the new). Pretty fun and awesome, especially when they make them look like politicians or unlikable characters from everyday life.
6) There is so much more I am missing, so I suggest you make sure you go to Bogota and discover how great it is for yourself! Use your common sense and enjoy what this great city has to offer.