One tool I use a lot for language learning and teaching is Google. It is a quick way of checking many things and is one of the most useful tools available, although it is not designed as a language tool, so its results should be treated with care. You could use any search engine, but Google is the one I use.
1- To check if a form exists
If you want to check whether a combination of words exists, just type them into the search box in double inverted commas, which locks the words together. This will show you whether they exist together. Look at the number of results; if there are a lot, then you can be sure the form exists. If there are none, or very few, then the form probably doean't exist.
2- Compare British and American usage
I choose the UK pages only and compare the search with the general result. This gives an idication of British usage against American, as American English is the dominant force on the internet.