The best thing you can do to help the dear house elves is to promote their recognition and welfare. Unfortunately, many wizards are still very much against freeing their fellow creatures, and prefer to still abuse them. This has led to brainwashing of the elves, which makes it difficult to enlist their aid in their own cause; indeed, many still shudder at the thought of being freed. One day, hopefully, they will be as grateful as the late elf Dobby for freedom. For now, though, they best we can do is try and gain support for our cause. Sponsor a cleaning of your House common room, perhaps, to show what dreadful lives these poor creatures live, or create a clothing collection so they can be outfitted properly and those that are accepting can be freed. You can also become a member of the Society for the Promotion of Elfish Welfare (S.P.E.W.) by sending two Sickles to our Treasurer, Ronald Weasley. This will pay for your welcome pamphlet, which includes more ideas, and badge.
Best of luck,
Head of the Office of Magical Law Enforcement