Gameplay Tips
1. Most important tip is to remember which are "your" units, i.e. the ones you are building and upgrading in between battles. Do all you can to minimize their losses. Other forces that are dispatched to aid you should be detailed to do the heavy lifting - up front taking the losses while your chrome-plated veterans in 1st Corps hang back and smother the enemy with overwhelming supporting fire. In your first battle at Phillipi, "your" units are Woods, Scales, Loomis, and Walton, so have Zook volunteer to take the van when crossing the bridge.
2. Save your game immediately after you win or lose a battle. Once you "Apply" an upgrade, you can't change it, so having the ability to return to the state immediately following battle exit allows you to correct mistakes you may make in the in-between Army makeup sessions. For instance, upgrading a 1000 man Brigade by buying fancy weapons while simultaneously adding, say, another thousand veterans can easily drain $30-40,000 with a single click. Oops.
3. Selling captured or obsolete weapons is a good source of money. Just be sure you won't ever need them as you only get half value when you sell.
4. Be careful when setting up artillery brigades, as limited inventory can make it difficult to switch weapons. Free cannons, either provided by government or capture,, are great and I'd recommend using them whenever possible.
5. You'll want to play around with the effects of adding veteran versus green troops. One thing to be aware of is that Veterans will maintain the "quality" of the unit. Green recruits will lower it. Adding enough green recruits to make a "starred" unit lose it's "perk" will cause a large downward quality shift, so you almost certainly don't want to do that - stop adding green recruits and start adding veterans. Remember you can add troops numerous times to a Brigade - add some vets, them some green , then more vets, etc.
6. Each Corps can have a supply level set, and thereby receive a supply wagon. If you're fielding multiple corps in a battle, make sure they're all supplied!
7. You can move Brigades between Divisions, and between Corps. Just pick it up with your mouse and move to where you want it to go and drop. You can also move whole Divisions between Corps. You will need an open slot where you're trying to move to. The game seemingly arbitrarily decides which of your Brigades it will bring to a battle with reinforcements. For instance when you get to Crossroads you might have a 12 Brigade 1st Corps but you can only put 9 Brigades into that fight. You do get to choose which of your 12 Brigades you get to start with (I think it's four or five?), but the balance of the 9 you get to bring as reinforcements will be decided arbitrarily by the game from all 7 or 8 remaining 1st Corps units. If you stick the extra brigades you DON'T want to have fighting, in your 2nd Corps so you can concentrate on buffing the nine you DO want to bring, you can then be positive that all your upgrades will find their way to the fight.
8. Reputation has 3 different uses. A. It provides additional morale to your entire army when at a high enough level. B. It's another resource you can use to request additional men, money, weapons, or officers. C. Most importantly, it determines your success as a General and if it drops too low you can be relieved of command and the war ends early. Typically, I only request resources prior to going into a major battle such as Shiloh. These are critical fights I want to have the best chance at winning, so using some of my rep to strengthen my army is a tradeoff I'm willing to take. Especially if I may encountered recent setbacks. Putting the best weapons into the hands of my most experienced brigades is important, and early on sometimes the best weapons are only available in large quantities by requesting them (Such as the Lorenz rifle). If you're confident in your army, then you can leave your reputation as a morale booster. Also, by not using reputation you're building it up in case you suffer losses in the future. Too many losses and your rep drops to 0 or negative, and you are relieved of command. So having extra rep allows you to suffer a string of defeats. Otherwise, one loss at a major battle could send you packing!
9. When your army is small, stick to infantry brigades as much as possible. This is the backbone of any defensive or offensive action. Cavalry are very useful for scouting and cutting down pesky skirmishers/artillery, but generally cannot defend against infantry brigades. Skirmishers as a separate brigade are useful to arm with sophisticated rifles that you normally can't get with large infantry brigades. But again, they are still skirmishers and not meant to attack/defend positions and hold them.
Armory: As you fight battles, your army will fill up with captured weapons. You can pre-purchase weapons here to keep in store, or sell weapons for $. Typically though you don't need to buy them here. When creating a new brigade, it'll show you how many rifles/cannons you have in your armor and how many you can buy. Anything you have to buy will significantly increase the cost of the new brigade. $10 per farmers rifle x 1500 men will cost $15k just to arm them (unless you have economic skill that lowers costs). So it's beneficial to arm your new brigades with captured weapons.
Barracks: Officers are a key component to your army. From your Corp commander, to division commander, to your brigade commanders. Higher level officers provide higher command and efficiency bonuses to everyone under their command. A Major, for example, will have a difficult time keeping a 2,000 man regiment operating efficiently. In this case, it's better to put at least a Corporal or higher in command of such a brigade. Wounded officers will remain in your barracks until a specific campaign is over, then they recover from their wounds and can be used again. Dead officers are dead.
Skills: When you win battles, you gain skill points. This is where you can further define the type of General you are. Keep in mind that Army Organization is a unique skill out of them all, in that when you get to larger battles (Such as Gaines Mill) you can bring 3+ Corp to such a battle. While that isn't necessary to play that battle, additional Corp allow for flanking attacks and mid-battle reinforcements. If you decide on having less Corp, but far more experiened/well-equipped troops, you can play that way too in most cases. Finally, don't feel like you need to always max out your brigades to maximum # of men. If you have 1000 veteran troops, adding 1000 rookies isn't always the best course of action. It may be better to create a whole new brigade of 1000 men, to provide additional brigades in a battle to help with flanking attacks, etc.
10. Cavalry - There are two types depending on what you arm them with. All Cav work best in open areas when mounted. Cav armed with a pistol and sword (the cheapest ones have the highest melee) are pure melee and cannot be dismounted. These are great for sneaking around behind enemy lines and attacking undefended artillery, supplies, and even officers. They also can wipe out enemy skirmishers if they can catch them. Keep these away from enemy infantry brigades that are at full moral or full strength. In addition to their raiding capabilites, Melee Cav can be used in large numbers (500+) to attack and wipe out routed enemy brigades of up to two or three times their size. They can be the Anvil to your Infantry's hammer. As enemy brigades are routed, your Melee Cav attacks from the rear and sides and will do an amazing amount of damage (I had a 700 Melee Cav unit completly destroy a routed 1700 size brigade). This only works against routed brigades. If they are not running, the enemy will shoot your Melee Cav to pieces. Note, this gets easier as the campaign progresses as infantry switches to rifles with less melee strength, thus they are more vulnerable to Melee Cav when routed.
Cav armed with carbines are more or less mounted skirmishers. They should never engage any target while mounted. You should dismount them and have them fight as skirmishers. Think of thier ability to mount up as a way to move them accross the battlefield faster, this makes them ideal for scouting. But as soon as they come under fire, have them dismount. Also, keep in mind that Cav units are expensive becsuse you have to pay for thier horses too, thats why their price is so high.