This is my first guide so general information is probably going to have some holes which I'll have to address once someone points that out in comments, be nice. :'(

Solo queue Nasus has been very rare lately and for a good reason - good old Nasus builds no longer work because of difficult laning phase. This guide is mainly about how to make Nasus viable in solo queue.

Here are the main issues I usually have versus difficult match-up for Nasus: 1) he's consistently under his tower and can not do a single thing; 2) he's weak for first 5-6 levels and opponents can basically do whatever they want; 3) he simply could not push the lane to save his life with mainstream guides.

This build is probably going to take some of the fun away as he will deal much less damage that everyone's used to, however, you'll be extremely annoying in team fights and you actually won't have to hug your tower(or even lose it).

First one is versus champions that can spam long range spells and deny your Q farm and push you.
Second one is versus melee champions that you might have a hard time to lane against.

Anything that helps you in early game can be used for runes to be honest because that's the main problem for Nasus.

I feel like this is a preference thing more than anything.

The exact build order will vary from champion to champion and player to player, but that's the general idea on what to buy.

I feel like this is the most important thing to go over for Nasus. If you get a match-up where you can max Q first, you should. You will benefit from it greatly and your team will thank you for that. But if you face (1.) ranged spell users or (2.) melee champions that are stronger than you early, by following the skill sequence I do, you will have much easier time farming.

About (1.).
Basically, you can not farm your Q with out losing chunk of your health each time, period. Instead of crying about that, your E does the farming for you. It actually does a lot of initial damage once you level it to 3 so you can farm with E very easily. Also, it's ridiculously good for pushing.

About (2.).
Anyone who depends on consequent auto attacks gets completely screwed. They can not do anything against you. Once you hit 6, anyone who usually could kill you with ease now is in a lot of trouble, too, because you now have 70% slow with 13s cooldown; anyone diving you will commit suicide; ganking you becomes ridiculously hard.
The idea behind this is to farm your Q as much as you can but I level E second because at the time I'm done leveling W I have plenty of bonus attack damage and cooldown reduction that I don't really need to level it for that, and E takes off their armor for your Q + allows you to push and do extra damage.

I use ghost and teleport/ignite, though it could change depending who you are facing.
+

This way Nasus has become an utility tank who constantly slows top priority target. With 40% CDR and early maxed slow no one is going to run away from you and if your opponents depend on a DPS champion you're just going to slow them and make them useless. Best thing about this is that you are Nasus - you carry and not get carried once it gets to late game. Although you are not going to do as much damage as you would normally, I felt like I had to address the skill sequence so we see Nasus a lot more, because he is still one of the top late game champions in entire game.