Ace + Rai
Here are some tips for Newbies like myself:
1. Get the Research Skill as early as possible. It will help eliminate one suspect. This will also mean that instead of asking for an alibi which will obviously not be verified, you can ask the suspect more details about the real killer instead.
2. Always make sure you have extra cash on hand. Three failure will mean the end of your detective. So by the time you have 2 failures, make sure you have some cash to pay off the Shady Character to clean your record. The fee increases as your experience grows. Sell equipment if you need cash.
3. Most of the Special Equipment that organizations sell may be had for free whenever you complete favours. Buy equipment only when you have lots of spare cash or when you have no false accusations.
4. Dies Arcanum Brotherhood or The Order of Socrates or La Cosa Nostra? Each will teach you one and only one skill. Go for La Cosa Nostra and its Safe Cracking Skill only IF YOU ARE SUBSCRIBED; otherwise, it is a totally useless skill. The other two organizations can provide skills that subscribers and non-subscribers alike can benefit from.
5. Choose Sweet Talking or Interrogation first then Rule Bending or Intimidation. Get the smarts, advanced & lockpicking skills a little later. Unlike CSI, the evidence alone can NOT nab a killer. Here, the best way to be sure is by getting at least two witnesses to name the killer (regardless of what the evidence says). Sweet Talking or Interrogation will help you weed out names, motives, and the identity of the actual killer. Rule Bending or Intimidation is to be used for townsfolk so you can verify alibis and check on evidence.
Of course if you cannot get 2 witnesses, you'll have to take your chances with the evidence.
6. Don't take Larry /Lucy unless you have lots of extra cash and have no false accusations.
7. If you only have 1 or 2 suspects at the start, ask first if they know of others who have a motive.
Just to clarify (yeah, some more)
#3: the equipment that the factions sell cannot be gotten from favors or AI cases. Sometimes, *comparable* equipment can be found in favor and AI cases rewards, but not the same equipment
#4: Safe cracking is only useful if you are subscribed AND in an agency AND treasure hunting. And even then, it is only necessary for 2 or 3 people in an agency to have it. So check with directors, etc before you buy this skill since it simply might not be needed.