Well, you do your best. What other options are there? Even a WAG is better than nothing. Aftrer a while one can guesstimate portion size at least somewhat accurately. Choose the closest generic item in the database if you're unsure about the actual ingredients/cooking methods.
If it's at a restaurant, many have nutritional info on their websites.
If it's at friends/family, I wouldn't be shy about asking about ingredients/cooking methods (i.e. fat added in cooking).
Personally, if I'm going to be away from the computer for more than a day I write down my foods on a memo pad and enter them later, giving my best guess as to portions and ingredients.
In any event, I don't think I'd leave a day empty as that will skew your nutrition, calorie balance, etc.
PS One option for "pot luck" type get togethers is to simply eat what you brought. This is what I did yesterday at the family Christmas gathering. I made turkey chili and that's what I ate so I knew exactly what the ingredients were.
47 M 5'8"
May 4, 2010...... 440? lbs. (Start FitDay Size 60 Jeans)
June 19, 2010.... 393 lbs. (First Weigh-in)
June 19, 2011.... 229 lbs. (164 lbs. gone in one year :-)
Current Weight... 185 lbs. (Size 36 Jeans)
Next Goal 169 lbs. (07/04/12)
Ultimate Goal 165 lbs. (12/31/12)
The best exercises for weight loss are Fork Putdowns and Table Pushaways.
Last edited by mecompco; 12-26-2010 at 10:33 PM.