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This is a little vague... As this greatly impacts the topology, do you have any specs this VCO must conform to? But as a general statement, just look up ring oscillators and LC oscillators to understand them first, then choose whichever one you feel will meet the requirements.
Well, if you wish to use the varactor for tuning, then simply use an LC oscillator, or a colpitts. It is best if you have some model for the varactor, so you can scale it accordingly to match calculations.