Hotel buffets

Just estimate. I wouldn't bring a scale, but a smart phone or a pen and paper to keep track of what you're eating would be a good idea. If you try to remember later, you'll forget half the stuff you put on your plate.

If you're going to the omelet station, you'll be able to see how much oil they scoop into the pan (or ask them to use cooking spray). You can estimate whether it is a 2 or 3 egg omelet. You may not have the exact grams of each piece of bacon or sausage, but you can look up calorie estimates for bacon by slice or sausage by piece.

Here's a link to some handy ways to estimate portion size although there are tons of different ones on the internet: http://www.shape.com/healthy-eating/diet-tips/simple-tricks-estimate-serving-size