By fighting. That will increase your levels in different skills, which will in turn affect your combat level. Note that the higher you are, the slower it will be to advance.
By using the highest level spell you can. Higher level spells give more experience.
Your able to get your attack up fast if you attack and kill animals or people above your level you gain more experience. When I played Runescape I used to do this alot. It's great fun isn't it!
I assume you want to level up combat. Same as in the paid game - fight a lot. Your combat level is also influenced by your prayer level; but in f2p, your fastest option is burrying big bones, which is still rather slow.
You can level up fast by training a specific skill and focus on training that skill. Some people like to do mini games for the experience.
do quests
For non-members, burn yews. For members, there are higher-level logs; you can also do the minigame "All Fired Up" for some fast experience.
killing Moss giants my help you level up a tad bit fast for your current attack level.
to change your stats on runescape all you have to do is level up.
by killing monsters
add friends and make games.
Pest Control minigame. You get xp from the points really quickly if you find a good world. Try doing slayer too. 2 birds with 1 stone that way. Or dungeoneering.
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