best way to retrieve data using multiple parameters in Cassandra?
This really depends on what other queries you're planning to execute - in Cassandra you need to model data around your queries.

For your specific question, you need either secondary index on userid, and do search (there are also some limitations there), or build second table with composite primary key consisting of userid, date, id - this would be especially useful if you'll have query "Show me all blog posts by this user".

Doing ALLOW FILTERING is generally is not recommended, because it may cause scanning of your whole cluster.