At level 1, play respectfully. If he takes W at level 1, he may look for an early engage and force you to blow your Flash. He tends to do this against utility Supports when they walk forward to harass.
Play towards the opposite side of the lane at all times. This will make it harder for Rakan to get a successful engage on to you or your carry.
If Rakan misses his W, you should try to abuse the cooldown and play aggressive. Getting him low will make it incredibly hard for him to use his W for the second time.
Avoid grouping too closely as it will allow Rakan to get a good Ultimate R off and he may be able to CC your whole team. Play slightly apart when possible.
Do not fight inside the jungle or around objectives when Rakan has his Ultimate R up as your team will be grouped closer together. Remember, being slightly apart will make it harder for him to get a multi-person Ultimate R.
Bursting Rakan down as soon as he engages is highly favourable. As soon as he activates his Ultimate R, try to CC him and burst him down so he is unable to get a good engage off.
Rakan has a strong level 1. Watch your positioning as he may look for an aggressive play at level 1 with his W and force you to blow a Summoner Spell. Similarly, watch out for his level 2 all-in.
When Rakan has purchased Mobility Boots, his roaming potential increases substantially. Ping whenever he goes missing as he is a very good roaming champion.
Rakan is really good in the mid-game and in team fights. Expect him to engage as soon as somebody walks out of position.