I often encounter nouns that I hear of for the first time, and I can not determine which syllable to stress. Unfortunately, I can not find most of these nouns in dictionaries to check the stressed syllable. I am not talking here about nouns of Latin or Greek origin nor about nouns of German origin but about nouns that are most often proper names, brand names (food, drugs..) which are invented only for commercial reasons, trademarks, names of foreign places, cities, rivers, people,... etc.
In English, the rule for the stress position in these nouns is there is no rule, and there is a very high probability if such nouns are given to English native speakers, they might come with very different pronunciations assuming that they have never heard of such words before.
Examples of such words:
Drugs brand names: Altace, Amaryl, Calan, Imitrex, Mevacor, Prilosec, Zoloft,..
Drugs generic names: Zolpidem, Verapamil, Warfarin, Venlafaxine, Fluticasone,..
Names of Chinese cities: Lhasa, Guangzhou, Chongquing,..
How can native speakers predict the stress position in such nouns (that they hear of for the first time)? Is there a tendency to stress the first syllable in such words? Is the stress position arbitrary? What would you advise me to get the stress right in such words?