This is a off-tank/dps champion guide. I am not trying to build him as a tank or as a strictly dps dealer. If you are looking for those guides then perhaps you might check out other very well made guides on this site.
I have used the other Nasus guides on mobafire and found that none of them suited my style of play. Yes, players have particular styles of play. If two players are put in the same position with same heroes, items and the like, they will make different choices. This guide suits me and hopefully aids you on your journey to having a viable Nasus build.

My above build has Large base health and a decent showing in damage output. What does it not have? Armor and negation. If you find yourself focused, you MUST build some negation. You are a off-tank/dps that has to get in the middle of the fights to be useful. Please build accordingly (look at item section).

CORE BUILD
Mercury's Treads + Sheen + Warmog's Armor + Atma's Impaler

Seriously, you MUST use your brain. Look at their team makeup at loading screen or look at who is carrying their team on scoreboard. Pick your items accordingly. Do not flame me because you did not purchase anti-carry items.

Tanking VS Casters
Banshee's Veil
Force of Nature

Tanking VS Physical DPS
Sunfire Aegis
Randuin's Omen
Frozen Heart
Thornmail

Your Damage Output
Trinity Force (in the above build)
Atma's Impaler (in the above build)
Zeke's Harbinger
Bloodthirster
Youmuu's Ghostblade

Other
Aegis of the Legion (Very useful early game before Warmog's Armor)
Guardian Angel

I have showed you the Two Summoner Spells I typically play with.

Teleport / Ghost

I have chosen Teleport over Exhaust because I play a lot of solo Ranked games. I can not depend on my teammates because I do not personally know them. If I know the group of guys then I will probably go...

Exhaust / Ghost

Just be sure to change the masteries accordingly.

I believe Nasus is a solid choice in a 1v2 lane. I think that Teleport especially helps out because you can blue pill (recall) and be back in lane without lose of time/experience. REMEMBER your job is not to rack up kills in a 1v2 situation. Of course, if they offer their lives on a silver platter then by all means accept the gift. You must understand that if you die in your lane then it has a huge effect. They will close the gap, even up or heaven forbid pass you in levels. Your jungler (assuming you have one since your 1v2) will have to cover your lane and he might not be in a position to do so. Not to forget, your tower will take damage because you were so greedy to get first blood or improve your KDR (kill death ratio). Seriously, your death for one kill is NOT an even trade for the above reason and they will probably both get moneys for your death. Be the smarter player.

I also am an advocate of Nasus being in a 1v1 lane. This will provide you with ample opportunity to build your Siphoning Strike. When and if you are the subject of a gank, you have a decent set of skills to sustain your life. Wither the attacker and Ghost yourself back to safety.

I like 1v1 Nasus but i do NOT think he is a center lane starting champion. That is usually held by your dps (damage per second) carry ( Ashe..ect).

Do not only last hit with Siphoning Strike. You will find yourself short on funds if that is the case. Do your normal last hitting (not hitting minion till it will kill them) but pop Siphoning Strike when its up for the last hit. Dont walk around with it glowing but activate it on your last hitting swing.

Nasus level 6 ultimate is not very impressive. It will not make a huge difference like other champion's ultimates. If you do not find a way to make a clear and easy kill with it ( Wither target/ Spirit Fire/ Siphon Strike / Fury of the Sands) then i advice you to use it to pick up a easy blue buff. Just pop Fury of the Sands, Spirit Fire/ Siphon Strike the bad boy and last hit his goons with Siphoning Strike and you will be doing dandy. Have fun spamming Spirit Fire. Once you reach level 11 and have your upgraded ultimate then enjoy the power it gives you.

In team fights, Place your Wither on their DPS carry! It reduces his movement speed AND his attack speed. If you opted for Exhaust then place it on their DPS carry after Wither has worn out or shutdown another DPS carry with it. This will greatly help your team in team fights.

Place Spirit Fire in team fights. It reduces the armor of their players allowing your DPS carry to flay those insolent adversaries.

I highly advise any Nasus player to watch Hyfe's amazing YouTube Nasus series. Expertly well done.


Link to his video