Reddit mentions of Keys to Teaching Grammar to English Language Learners: A Practical Handbook (Michigan Teacher Training (Paperback))

http://www.amazon.com/gp/aw/d/0472032208/ref=redir_mdp_mobile

Keith Folse's Keys to Teaching Grammar to English Language Learners: A Practical Handbook is excellent and will hit almost everything you need to teach about grammar. It's detailed, provides activities, and is really, really good at tenses. The charts in here are amazing and will make sense to both you and your students. Also, there are "Hot Seat" questions in the back that are great for preparing for questions that often stump many ESL teachers.

I took a class on teaching ESL, taught by our college's ESL specialist. This is the book we used: https://www.amazon.com/Teaching-Grammar-English-Language-Learners/dp/0472032208

It's pretty good. It covers the most common issues/sources of confusion that you'll encounter with ESL students, as well as how to explain them. When a student asks you why what he/she wrote is wrong, and why it should be the way you say is right, it lets you say "Because XYZ" instead of "That's just the way it is".

One example covered in the book is prepositions. To an extent, they make sense. Especially with directional prepositions. But a lot of situations require certain prepositions for no logical reason. Like, you wouldn't say "I believe of you". But why is "I believe in you" better? But at the same time you say "I'm thinking of you" and not "I'm thinking in you". This can be incredibly frustrating for students. But letting them know that there isn't really a reason and sometimes they just have to remember can make them feel better, as opposed to trying to figure out the logic of rules that don't really exist and that no one can seem to explain.

Reading helps a lot. Keeping simple books around would be great. And/or books that are written in two languages. Like books where the left page is English and right page is Spanish. If these are hard to find for some of the languages, you could make your own by printing out short stories in both languages. Or even using google translate to get a copy in the student's primary language.

Encourage them to consume their media in English. English movies, music, shows, etc. Also, all Netflix original shows (or at least most, I think it's all) will have dubs in Spanish, and will have captions in multiple languages. Watching a show in English, with captions in your language to help you figure out what you don't understand, can go a long way. The opposite is true too (watching in Spanish with English captions).