How to Store When Uncorked

[jibtalker]

Hello All, I just started getting envolved with wine and have many questions. I just bought a bottle of CK Mondavi Merlot and a Fetzer Johannisberg Riesling, but I'm not to sure what category of wines need to be refrigerated when opened and what can be stored at room temperature? (I don't have a wine cooler yet.) I realize this is a broad question and can depend by vinyard, region, year etc. Until I get a wine cooler what wines will have to be refrigerated when opened and how long will they last once opened.

Thanks,
Jibtalker