correct answer may vary with climate, winds, soil type.
position with nails, secure with stainless steel deck screws unless you
are in a dry climate use coated screws. lag bolts will add that
strength you want.
for climbing or high wind/hurricane area concerns and fence permit
requirements you'll make sure the posts are sunk below the frost line
with a bag or 2 of concrete per post or whatever is required in your
climate and soil condition and town. good fences make good neighbors,
go visit yours first after you take your property survey to the
building inspector and he tells you how high and how far from the
property line, how deep the posts, etc.

wrote:
I want to make a 6' tall, wood fence, on 8' centers, using 4" x 4" wood
posts.

When I attach the 2" x 4" horizontal members to the post, is it best to
use lag bolts, decking screws or nails?

Thanks.

Lewis.

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