I like reading build guides occasionally, but there's been something glaring in almost all of them which as bugged me.
For skill orders almost everyone considers one skill you max at 9, one you max next, and a follow up one for end game. I've always found this horribly inefficient for most champs that I play.
Take rammus for instance. I think only 1 level of Q is sufficient for most of the game, but when choosing to level up taunt/defensive shell I level then in roughly a 1:1 ratio (depending on feel of the game). Taunt for instance scales linearly from 1-1.5-2... etc. So the 2nd level's duration is 50% longer than the first, and the 3rd is 33% stronger than the previous level, and the 4th is 25% stronger. You end up getting diminishing returns. For the shell it also scales linearly in a similar fashion: 50/75/100/125/150 and returning 22/28/34/40/46 (+) magic damage to attackers. Isn't it more practical to have level 3 of each of these rather than 5 of one and 1 of the other? It's not like the difference between 100 and 125 magic res/armor and 6 more damage return is going to be as game breaking as an additional 33% duration on your disable.
Anivia is another similar hero though I like to play her as a 3/3/3 type at 10-11ish (obviously grabbing ultimate when it becomes available. The stun duration doesn't increase, but it's damage certainly does and it's cd decreases (iirc). My reasoning for her is a little different than rammus though. There are some games where I notice I'm having a difficult time following up my stuns with my E because of fear of enemy cc or whatever so I'll get more points in stun rather than E. Also, the utility of the wall with a 600 distance vs a 400 distance is 50% larger on top of having a reasonably shorter cooldown. You can cut off enemies in much more different parts of the map with a 600 wall vs a 400.
The list could go on because come to think of it I play most heroes in this respect. Orianna because her attack command lowers the cd, the slow gets much better, and the shield at higher levels can save you or teammates who otherwise would die. Sona is another one since her w is worthless until level 2 as it gets a 100% increase from 1 to 2, but then begins to taper off a bit and doesn't scale tremendously with AP. Meanwhile aoe MS can win a fight and her 'nuke' song can be great for harassment in the early game.
Point being, I'm not a huge fan of maxing one skill first on a lot of champs. The game often dictates the use of every single skill at different times so I'd hate to have soemthing useful underleveled in a key situation because I wanted 20% more damage on another move vs 50% longer disable on another one. OFC there are some heroes where it seems useless to take things beyond one point (jannas tornado and lux's shackles off the top of my head), but for the most part going for 5 points of something at level 9 leaves you a lot more exposed than a 3/3/3 on a lotta champs.