If you use tor browser and your ISP blocks Tor, you can easily use bridges within tor browser. You can even use a pluggable transport such as obfs4proxy to avoid detection from a network observer at the application level.
If you are running tor on the command line, for example on a linux server, you can still use bridges and pluggable transport:
First, get some bridges
Second, make sure you installed tor and obfs4proxy;
Then, edit /etc/tor/torrc and add UseBridges, ClientTransportPlugin and Bridge lines:
UseBridges 1 ClientTransportPlugin obfs4 exec /usr/bin/obfs4proxy Bridge obfs4 192.168.0.1:1234 ABCDEFG cert=123456789abcdefg iat-mode=0
If you don’t need obfs4proxy, you can just use a bridge line like:
UseBridges 1 Bridge 192.168.0.1:1234 123456ABCDEF
You can put several bridge lines, in case one does not work.
After you start tor and make sure it works, you can use it with torify command or whatever you like.