If you have a cold, flying will probably make it worse - ideally you should delay the trip. Get a good night's sleep just prior to departure. There is much debate about whether it is better to fly eastward or westward. It may be largely a matter of personal preference, but there is some evidence that flying westwards causes less jet lag than flying eastwards. Again it is largely a matter of personal preference based on experience.
Most travellers think daytime flights cause less jet lag.
We note that more daytime long haul flights are being added by major airlines. The dry air in aircraft causes dehydration. Drinking plenty of non-alcoholic fluids counters this. Water is better than coffee, tea and fruit juices. Alcohol not only is useless in combating dehydration, but has a markedly greater intoxicating effect when drunk in the rarefied atmosphere of an airliner than it does at ground level.