Of course, refining the precision of language is done through lots of exposure to, and use of, authentic language – not decontextualised grammar drills. That said, giving your students ‘Bell Work’ (a small task they do as they enter the classroom and settle for the lesson, which needs little or no introduction) that requires them to think about grammar and syntax and discuss with their talk partners about solutions to a grammar-based challenge is no bad thing.
The attached pdf contains a host of daily activities that you can use in your class. Basically, each day the students have to manipulate a sentence in a different way; for example add an adjective, up-level the verb and so on. The pdf gives you the task for each day and sentences for your students to work with. There are 30 weeks worth of activities!
I would recommend making this richer for ELLs by asking them to discuss their responses with their talk partners and critically evaluate those responses. You can very easily adapt it to suit your age phase or subject.
Let us know how you get on in the comments box below.