I love grammar! Knowing and using grammar is like putting together a puzzle. If you put the puzzle pieces where they belong, you can see the picture. If the puzzle pieces are in the wrong place, you won't be able to understand.
How much grammar do you know? Here is a 58-question grammar test that can give you an idea of how well you can use English grammar. This is one of many grammar and vocabulary tests that can be found on the a4esl.org website. The tests on this site have been created by ESL teachers from around the world.
The Study Zone from the University of Victoria in BC has very good grammar information and some online exercises to try.
The Guide to Grammar and Writing is a comprehensive American site that offers a lot of information on specific grammatical topics, as well as PowerPoint presentations, online quizzes, etc. Here's the index of topics. The information is very detailed, so you may find that there is too much information on this website. Remember, this website is designed for college students, not ESL learners.
The Core and Quirks of English Grammar uses visual imagery to explain the core (the basics) and the quirks (the exceptions of English grammar.
The OWL (Online Writing Lab) has been a favourite for teachers for 20 years.
Verbs
Verbs often followed by a to-infinitive: Some verbs in English are often followed by a to-infinitive; that is, by to + the base form of another verb. How can you know which verbs behave in this way? The best way to learn this is to listen to and read and use English as much as you can, and notice which verbs are often followed by a to-infinitive. Here are some websites to help you start thinking about these verbs. Please note that I am not suggesting that you try to memorize these verbs!
English Page is a good website for reference. It has online exercises that you can try for different grammar topics.
The British Council Learn English website has good information and some practice activities.
Learn English has some good basic information. There are other pages of this website that you can explore as well.
Understanding the -ing form of verbs
English verbs with an -ing ending can be either a present participle or a gerund.
Education First: Passive Voice (information)
Guide to Grammar and Writing: The Passive Voice (information and quiz)
English Grammar Online: Passive Voice (information and exercises)
The Study Zone: Introducing the Passive Voice (information and exercises)
The Study Zone: Passives - What, How, When (information and exercises)
English adjectives have an order. Fluent English speakers put their adjectives in the right order without thinking about it. The Learning English website of the British Council has good information on the order of adjectives.
Edufind has a clear explanation with some examples. They have a long list of basic grammar information as well.
Comparatives and Superlatives
The British Council also has excellent information on comparative and superlative adjectives.
Education First also has a clear explanation of the form, meaning, and use of the comparative and the superlative.
Cambridge Dictionary also has good information on using adjectives for comparison.