In most cases it's impossible to guess the gender based solely on the nature of the object. It's a matter of outlook. For example in Russian "death" is feminine (and is often described as an old woman with a scythe), in German "death" is masculine. Russian "дерево" (tree) is neutral, "ветка" (branch) is feminine, "лист" (leaf) is masculine. Why? Who knows..

BUT...

Often you can tell a gender of a nown looking at its ending:
female - -а, -я
neutral - -о, -е
masculine - consonants

There are exceptions to this rule, but not too many, and you'll be able to memorize them. For example "папа" and "дядя" (dad and uncle) are understandably masculine, despite ending with а/я.

It reminded me...
Most diminutive names (both male and female) end with 'а' or 'я', and it often causes confusion among non-Russian speakers. Famous Nikita (with the stress on i) is a male name ONLY in Russia and CIS countries, as are some other Russian male names that are used as unisex in Western countries. In the movie "Gannibal rising" Gannibal's little sister was named Misha, which was a terrible blooper since the action took place in the USSR (Misha is short for Michael and is also a strictly male name here).