1.Enemy lane having high armor through items and passives? MAX YOUR TEMPEST FIRST THEN.
2.Enemy lane stacking the crap out of sustain? MAX YOUR SAFEGUARD FIRST THEN
3.Enemy lane is a squishy ranged champion? MAX YOUR SONIC WAVE FIRST THEN
Hitting your Sonic Wave in any fight is crucial, the damage this spell can do when followed up with some auto attacks and a Resonating Strike is completely absurd. Even more critical to hit it on enemy carries late game. Be experimental about smart casting and manual casting this spell, I have resulted to using manual cast when I want to have a precise shot since this spell has quite a long cooldown.
Sometimes you will want to follow up your Tempest with a very fast Cripple since the range of the Cripple got reduced, also allows you to trade hits with champions such as Jax, Irelia and various AD carries.
Your Dragon's Rage isn't always meant to be a execute spell, you can use it to CC important targets, or better yet. Knock a squishy champion out of position. This spell has many uses, it has high damage with strong CC potential while also being a incredible disengage spell.
Safeguard can be used to jump to wards, Jarvan IV flags, Shaco Boxes, Zyra plants and anything that is allied and can be targeted. Using this knowledge to get in position to gank faster by jumping to a allied river/lane ward can be very potent. Also if your lane has a gap closer you can use them as a relay point to get closer to the enemy lane you are ganking.
Using Dragon's Rage on a champion when they are inbetween Lee Sin and a very thick wall can allow you to get a Pseudo CC from the knockback duration. Use this to your advantage when getting a gank or when you are getting ganked. It will often make or break how the flow of the fight will go.
Lee Sin can split push very well during mid game if you have enough wards or a sightstone, you will be safe enough to avoid death and be strong enough to duel most champions. If you went a attack speed oriented build with Blade of the Ruined King + Trinity force then you will have much stronger split push and duelist potential.
When fighting in lane it is always best if you can get close to your enemy laner and using Tempest/Cripple on them before trying to go for a Sonic Wave/Resonating Strike when trading hits. If executed correctly you will almost always come ahead in trades unless the matchup is a sour one.
Usually when the laning phase ends and you build as a assassin bruiser, Lee Sin has the potential to kill most AD carries in one combo. Vayne, Ezreal and Caitlyn are most susceptible to this due to their lower base statistics. Try to cherry pick kills off them if you are confident you can tag them with your Sonic Wave/Resonating Strike.
If you are absolutely dominating your lane you should consider pushing the tower and either counter-jungling a bunch or roam towards other lanes. Lee Sin is well known as a strong ganking champion and you should utilize this even if you are laning.
Always make it a habit to buy one or two wards when you go back to base, the small gold spent is usually your life insurance that most champions cannot get. They can either help you be more mobile or just observant of everything that the enemy team is doing.
Lee Sin is a extremely flexible bruiser, you can build almost any AD item on him and also have the option to go a little tanky with almost all tank items being viable on Lee Sin. Experiment what you feel would do good in your lane matchup or for later on in team fights, you can learn many different things simply from building differently every lol power leveling game.
If you are doing very well in lane and have a jungler who can be the sole tank of your team then consider maxing your damage spells over safeguard, this will let you snowball much harder and farm faster than the staple