First of all, Go West of "Home" and search for Nurmof located in the Shield Shop.
Buy a Bronze Pickaxe for 1 Gp, and also buy a Rune Pickaxe for 20k.
Now head "South, West" till you see some rocks, The first 2 are Rune Essence.
Mine "EXACTLY" 189 Rune Ess, Congratz you can now Mine with a Rune Pickaxe!
: Getting the 99 Mining skill :
Now where making some progress keep mining Rune Essence till 70 Mining.
You will have PLENTY of Rune Essence now, You might sell it and make some cash.
Or you could keep it and use it for Rune Crafting.
Congratz you can now mine : Adamant Ore!
Now once you reach 70 Mining you may continue Mining Rune Essence ( Your choice ).
Or you may try the Adamant Ores, keep doing this till 99 Mining.
I can't really explain more at this point, I wish all of you the best of Luck!
Rune Essence = 5-10K ea ( I got told ).
Adamant Ore = 10-20K ea ( I got told).
1 Rune ess = 220 XP
10 Rune ess = 2200 XP
100 Rune ess = 22 000 XP
1000 Rune ess = 220 000 XP
10 000 Rune ess = 2 200 000
1 Mithril ore = 500 XP
10 Mithril ore = 5000 XP
100 Mithril ore = 50 000 XP
1000 Mithril ore = 500 000 XP
10 000 Mithril ore = 5 000 000 XP
So 99 Mining will probabbly give you alot of Money!