Galio is a mage tank designed to catch enemies, force them to focus you, and lead the team to victory. You have at your disposal: [b]The Stats[/b] By late game you should have over 2500 health points, over 200 armor, and over 150 magic resistance (and that is not including your [img=skills/galio/w.png], if you choose to buff yourself +90 armor and +90 magic resistance). This is still while building core support items (such as [img=items/sightstone.png] and [img=items/talisman-of-ascension.png]). [b]The Gap Closer and the Getaway[/b] The team will benefit from your [img=skills/galio/q.png], [img=skills/galio/e.png], and later your [img=items/talisman-of-ascension.png] to either engage or disengage. [b]The Ultimate[/b] The ideal way to fight any battle with an ally. Catch up, line up, and have them be distracted by your awesomeness as your teammates whittle down their health. The damage at the end of your ultimate [img=skills/galio/r.png] + [img=items/thornmail.png] can kill quite a few foes (including the enemy ADC).
Although [img=skills/galio/e.png] gives you and your ADC more movement overall, Galio needs his [img=skills/galio/q.png] to both harass and slow enemies. Early on, allied champions (especially your ADC) won't have enough health for [img=skills/galio/w.png] to make a large difference.
Be aware that you can empty your mana pool pretty fast. Use [img=skills/galio/q.png] to harass and prevent ganks. Avoid using [img=skills/galio/e.png] unless you are securing a kill (gap closer or the damage) or rushing to meet your jungler coming in for a gank. Stay near your laning partner and keep moving around to establish better positioning.
If the laning phase is still happening (but towards the end), start zoning them with your body and your [img=skills/galio/q.png]. Again don't use your [img=skills/galio/e.png] as you need that to get away or secure a kill. After level 6, you may be able to [img=summoners/flash.png] [img=skills/galio/w.png] [img=skills/galio/r.png] [img=skills/galio/q.png] [img=skills/galio/e.png] or [img=skills/galio/e.png] [img=skills/galio/q.png] [img=skills/galio/w.png] [img=skills/galio/r.png] the enemy ADC or to counter-gank. You should be actively warding Dragon and the river area (put a [img=items/vision-ward.png] in the bot tri-bush.
You are a warding machine (Ward Baron!!!) and you are always there for a teamfight (even starting it if need be). Allied champions have enough health points to receive your [img=skills/galio/w.png] if they are tanking. The movement buffs and vision should allow your team to pick off wandering enemies. Also, don't be afraid to ask your teammates to put down a [img=items/vision-ward.png]. They usually aren't cranky about your request if they have build at least one core item and are not full build.
You are usually the first person after the initiation. Use your [img=skills/galio/q.png] to slow \"target first\" champions or as many enemy champions as possible.