I'm also interested in how to restore damaged habitats. So consider the types of damage:
* Farming reduces nutrients and humus, often going all the way down until the land becomes unfarmable. This would logically be improved by applying large amounts of organic matter such as compost, fresh stall-sweepings, cover crops, etc.
* Tilling changes the soil structure. This one can largely be reversed by leaving the soil alone after the above nutrient repairs have been made.
* Species diversity suffers greatly and recovers slowly if at all. This might be assisted by replanting native species and perhaps capturing some fauna for redistribution.
However, the best approach is connectivity. Wild strips such as fencerows, grass-lined runways for water, and riparian zones around rivers make it much easier for wildlife to travel between larger sections such as parks or nature reserves. Nothing may happen for a while, but then this species or that one has a boom year. If the dispersing young have places to go, they will recolonize empty niches. If not, they get pushed out into inhospitable areas where they die.