Use side of house or garage. You can use strong fence post, and plant your own post across from it. You may also use available trees, or one tree and one post.
If there are'nt trees or usable walls, place two posts the correct distance apart and hang your hammock between them. Post must be 8 ft long and holes dug 2-3 ft deep so posts stand above grounds 5-6 ft. Use cement to secure.
From trees: Use hooks if trees can take them without damages; or tie rope around trunk or strong branch.