This is something a lot of english speakers have to deal with. There's no real "trick" to know whether a word is masculine or feminine. Although, as you get used to french, you may notice that some noun endings give off their gender. Ex: words in "ette" use "la"; like fillette, maisonnette, clarinette... If you speak a romance language such as spanish or italian, this might be easier to get used to. Also, some specific word groups go exclusively by one of the two genders (like all colors use "le")

It a question of gender . Some are female and other masculine. And it is only by practice that you can be used to know what gender it is. For exemple in German the gender are different from French.