Only visit sites that use HTTPS. HTTPS Everywhere is a great browser extension for this.
Additionally, DNSCrypt-Proxy will secure your DNS lookups, by using authenticated encryption.
If you're worried about metadata (your ISP knowing what website you're talking to), just use Tor.
Note that Tor isn't compatible with BitTorrent. If you're hoping to use BitTorrent without advertising your home IP address, the best solution is to set up a cheap VPS in another country and torrent from there.
For best results, only connect via Tor, and if you're especially worried, try to find a VPS provider that accepts payment in Bitcoin or something. PORTAL on a Raspberry Pi might be helpful too.
(If you're not using PORTAL, the commands
torsocks ssh user@server and
torsocks rsync -rc user@server:~/remote-directory ~/local-directory are your friends.)