Yan Lo is pretty straightforward, but it's his synergies with his ancestors that make him complex. Here are some things that I have learned outside of pullmyfinger.
# of Ancestors: This is key, one imho is to few, but more than 3 is too many. Since there are only 4, Chiaki, Izamu, Toshiro, and Yin, in general running all of them is risky. Keep in mind Yan Lo can only bring back one at a time, so model attrition is more important to Yan Lo than say, Nicodem.
Chiaki: While Yan Lo is a rezzer he does very little summoning. Toshiro, Molly, and Mortimer can be run with her and create some interesting synergies. Keep in mind a few things:
She can be given relics (getting Yins' relic is good with her harmless ability), but you lose that relic if she dies before being able to hand it off to Yan Lo. Her cleansing pulse can be used to clear the slow off summons, so delay her activation till after you're done summoning for the round (hence the synergies up top) Yan Lo isn't an undead or non-living model, so most of her other spells don't affect him, and unless you're against many non-living opponents, aren't going to be much effect either. Push Trick*: Pushing with her is pretty easy. Living Memories: Just make sure you don't Living memories before Yan has a chance to make them spirits.
*edit: Man, I must've been high when I wrote this part initially.
Izamu: Izamu's "reactivate" with Yan Lo and the spirit porter is probably his most powerful trick. Other than that he can be a corpse factory, by his death + only using 1 of the corpses he drops to resummon him. Keep in mind though that Yan can only Rebuild Izamu once per turn so that 2wd Izamu needs to be healed or protected in some way. If you have the cards cheat a severe damage and a free healing flip.
Toshiro: Toshi is great for his Damyio ability, but I like him for Eternal Servitude. Keep him in the back lines (4" away if possible) and use Reposition to keep him there. Yan Lo or Chiaki with Damyio is great, but you're not getting any conflict counters while Toshi is dead. Keeping him on the field to generate more PZ's is always the best bet. Also, PZ's are far better than Ashigaru, and start with at least 1 PZ in your crew to get the most out of Toshi.
Yin: Also great to double drop (reactivate) with Yan Lo + porter. Terrify is a tricky mistress, but can do some great harm to your opponent. Usually best with running Molly or Killjoy to give Anathema to. Yan with Terrifying and Anathema is only good late game with many chi points. Also, if you put Yin in defensive mode while in combat with many enemy models, and keeping him alive with Repair Corpus is a great way to control the field. Repair corpus only needs a 4:crows, so keep those cards in hand if you are working that strat. Another Strat is to maximise your WP tests every turn. Run Molly and Full Ash Yan, toss up Gnawing Fear, and keep making your opponent test vs WP. As many as you can, every turn.
For Yan, Shatter Reliquaries is his "life saver," but doing it will hurt. If you are in the position where you're needing to sac your relics to stay alive, you've already lost. Chiaki's is going to be the first choice and it just goes downhill from there.
Yans' Paths:
First 3 in Ash. Always. The regen is nice, but usually forgotten, its the 7df that you want. After that rush your next two points into Ash for Rigor Mortis.
Rigor, as any Nicodem player will tell you is going to be your most powerful asset. Drop a SS into it on their master in a crucial turn and watch the calamity ensue.
After that its really only a matter of preference. I usually keep going in Ash for Terracotta Curse if I'm playing Yin (as above).
Full Bone Yan is nice with Toshi, but with his Cb5 he really isn't that much of a powerhouse hitter. Keeping him back as support with 3+ Cb7 PZ's and Toshiro behind them is more effective.
The Path of Spirit keeps Yan around longer, and his "ultimate" in that path (Fury of the Yomi) is really nice, but to guarantee it going off with decent effect you need an 8:tomes and a 9:masks. Highly situational.
Run the Spirit porter. Even if he's never used that 2SS little bugger is really helpful. Just keep him linked to something in the back, or run him into blocking terrain. Either way KEEP Yan or Chiaki within 6" if him and you can run your ancestors anywhere on the board. Read Recover Lost Souls carefully, there is no range on its effect. Meaning... KEEP Yan or Chiaki near him at all times.
He's helpful with his push, that can be cast twice per turn, and his kill. If you want something to feel "death by Izamu" companion Yan, porter and Izamu, hit 3x's with Izamu, kill Izamu with the porter then resummon Izamu with Yan. Next activation Izamu can hit 2(3 times if you Chiaki companion and cleanse) again for some real damage.
He also can Repair on a 6:crows giving you +8 wounds per turn to work with.
Bah, I've given you so little, but I've already said too much.