There are two entrances to the Mining guild.
Firstly, to enter it from Falador, you can go down one of the four ladders in the Dwarven stronghold just south of Falador's east bank. To get there from the Ice Mountain entrance, you must head east, then south until you are passing the scorpions and king scorpions.
This is one of the best and safest places for free players to mine coal and mithril. Note: you are able to enter this guild at level 59 Mining by drinking a dwarven stout located in the Falador Pub.

The Dwarven stronghold above the Mining guild serves merely for decoration, and has no real use. As this entrance leads directly into the guild, if you do not have level 60 mining when you try to go down one of the ladders, you will be stopped by a Dwarf. The other entrance to the guild (underground entrance), is also guarded by a Dwarf.

The Mining guild is often very crowded as it contains thirty-seven coal and five mithril rocks. It is a great place to buy coal in large and small amounts. For more information on this mine, visit the Dwarven Mines mining map.