Question

 
Do you know someone (preferably available), an expert in kosher food, who could answer my questions and explain to me the rules according to which one should act? 
I travel from time to time in countries where there are no kosher restaurants or grocery stores, and I wanted to know what is permitted to eat and buy, what is strictly required by Jewish law, what is stringency, and what is leniency. For example, I heard that bread can be eaten in almost any place. But what are the conditions, etc. etc.? Is it permitted to eat avocado with olive oil and lemon in a non-kosher restaurant? And so on, many more questions.