The University of Alabama School of Law
Some of the commercial databases have introduced technology that creates citations that you can copy and paste into another document.
On Westlaw, when you're looking at the document you want to copy, one option is to look at the right side of the document for the icon circled in the example below. You will be given the option to copy the citation to the case.

Another option is to highlight the specific information that you are looking to cite to, like the example below. If you select "Copy with Reference," Westlaw will generate a citation in Bluebook format. If you clicking the dot icon to the right you can change the citation style if you need something other than Bluebook.

One option to copy the citation is to simply click the "Copy Citation" link found under the document name. This will bring up a pop-up window that you can use to try and make some adjustments to the citation before creating it.

Another option is, similar to Westlaw, you can highlight the information you want to use. A box like the example below will pop up.

If you use "Copy (Quick) : Standard" you'll be able to generate a Bluebook citation, however, if you click the arrow to the right you'll be able to change the citation style.
If you select "Copy (Advanced)," you will get the same pop-up as clicking the "Copy Citation" link at the top of the page.
Note: Always remember that you can't rely on the citations. You have to make sure you double check the accuracy of the citation.
If you go to LexisNexis, you'll see a link titled "Interactive Citation Workstation." If you select it, you will be taken to another page that has an option for "Student Exercises" to the left of the screen.

This will give you exercises for several different citation styles to practice.
If you go to the TWEN page, if you hover over "On-Demand Learning," you should see "Guided Exercises." If you hover over it, you will be given two options: "Research Exercises" and "Citation Exercises." You will be given a scenario and exercises that allow you to practice researching and citing various legal documents.