To get to the rulemaking page on the FAA website, hover over the Regulations & Policies tab at the top of the page, and click on Rulemaking.
In the box Top Tasks, click on the link "Find recently published rulemaking documents"
From there you can see the latest NPRMs pertinent to the aviation industry.
On the Federal Register homepage you can either browse for NPRMs, or search for specific topics. The green box has current issues, including proposed rules.
To search for an NPRM on a specific topic, enter your terms in the search box in the upper right of the homepage.
Choose Proposed Rule under Type in the filters on the left. You can also filter for agency, topic, and publication date. Click on the Newest tab to get the proposed rules still open for comments.
To comment on a Proposed Rule, click on the green "Submit a Formal Comment" button.
As with the Federal Register, Regulations.gov allows you to browse or search for proposed rules. The middle column has links to documents with comments due soon or ones that are newly posted.
If you search or if you browse, the results page looks the same. You can filter it to have only proposed rules with an open comment period. There is also an easy Comment Now! button for each result.