We use the apocalypse nigh and fall of man preludes together every time for a brutal combination. Both of them cause disasters in non-Shudde'mell games. Shudde'mell is one of our favorite ancient ones. Disasters may be one of the best things they have added to the game. It's crazy having a disaster kill one of your investigators on round 2. It's the best small box expansion IMO.
I have played EH for hundreds of hours and own every expansion. I currently have around a 70% win rate when I solo play (I control 4 investigators). This is even with choosing fully random investigators. Here are some tips:
- Pick an even number of investigators (4 or 6 is best). You can control multiple investigators per player since there is no hidden knowledge between players and it's cooperative.
- Focus tokens. Try to have at least one on each character at all times. Know when to use a focus token and when to hang on to it. Don't use focus tokens on tests where there's no fail penalty or the stakes are low. Blowing a focus token or two on trying to get an extra success during an acquire assets action is almost always counterproductive. When you fail encounter tests, you not only lose a reward, you often eat a penalty, which is why you should use focus tokens on these sorts of tests. There are also some events that require focus tokens to pass.
- Clues. Try to hoard clues but don't waste encounters picking them up off the board unless you really need to do it to solve the mystery or rumours. There are ways to get clues during the game outside of spending an encounter on it. Closing gates, acquiring assets, performing tasks, and investigator special abilities all can generate clues or spend other stats in place of clues. Don't waste clues on rerolls unless in some sort of dire circumstances or you're at the end of the game sitting on 10 spare clues or something.
- Tasks. Tasks can be a time sink or super useful depending on the task. Don't waste 6 actions on a courier run or treasure map if you can help it. Try to flip/spend them when you've supplied them three times if possible, that will give you the most benefit. In general, I avoid tasks or ignore them unless they're easy to complete.
- Acquire assets. It's an art form in and of itself. With the expansions added, debt can be a real game loser sometimes. Use debt sparingly and if you have a 3-4 influence character, it is usually worth it to spend an action clearing the debt before the next reckoning. Avoid performing acquire assets actions on your 1 or 2 influence characters unless you have a dire need of a specific item. Make sure the right items get to the right characters. Allies with stat boosts and re-rolls are extremely useful on investigators with weaknesses in those stats. Try to get everyone at least one decent weapon in case of ambushes.
- Dark pacts. In general, don't take them if you can help it. If you do have to take one and can't get it removed by 'Sanctuary' or some other means, be ready for that character or another character to be crippled or devoured. Dying before the dark pact comes due is often a good strategy. Don't waste actions to rest or improve stats on a doomed soul. Same goes for agreements. Agreements are almost worse because they are likely to kill your investigator and have double the chance to come due per reckoning.
- Buff your investigators. Work on patching weaknesses on your investigators via improvements and assets. You should be buffing up as much as possible the first several turns. Do not attempt difficult encounters such as strong monsters, sealing gates, or expeditions without first being prepared with nice equipment, spells, focus tokens, and clues if possible. Trinkets that help you pass any tests via re-rolls, adding one to a test result, or granting additional dice are incredibly useful. I believe the best item in the game is the lucky cigarette case. Spread nice items around. Weak investigators are a liability to the team.
- Know when to die. Sometimes an investigator will hit a patch of nasty luck. Failure after failure, tons of negative status conditions, weak items, lots of damage and sanity loss. Don't be afraid to send investigators like this into danger and get them killed. Wasting rest actions on a doomed investigator is usually a bad move. Keep the 'lead investigator' token on the weakest investigator, as mythos cards can frequently harm the leader. You don't want your most effective investigator taking needless damage or getting cursed during a critical moment in the game.
- Keep gates closed. Close gates when you can, as long as it's safe and you're prepared. If the monster's too strong for you, you'll just take damage and lose an encounter. Having more than three gates open is a bad sign. Having more than 5 gates open at a time is a very bad sign.