Sure! Regarding creating characters and using the party, they are very few things I do differently from when I play play-by-post games, actually. Mostly, I sometimes roll a dice to decide who will react to a given situation if I feel some characters start to overshine the others.
The main difference is on the DM side, about how to build the campaign. I run the game in Faerûn, using the awesome Forgotten Realms wiki [1] to provide material. I don't try to follow everything from it exactly, but this provides a source of outside content, so that when the party reach a place, I discover much of it as well. I have also a high-res map of Faerûn that I load in inkscape to put tokens on it to show where the party is, and what there is around.
I made myself a NPC generator, based on the suggested rules in the "This is your life" chapter of Xanathar's Guide to Everything, with personal additions for commoners' life. When my party reach a place, I'll generate about twenty characters, and look at their generated lifes. Quickly, there'll be groups of characters that have similar events in their life, and imagination will take the relay to explain those similarities and produce a story for them. I change everything I want in those characters, the generated content is just a suggestion, but I think randomizing the most things possible is key to keep entertained in a solo game - that and adding outside content you discover on the go. It allows to emulate the exploration aspect of a game as a player. Plus, as a programmer, building generators/randomizers is half the fun :)
There are also difference in gaming rhythm and splitting the party. Since I play alone, I can play whenever I want, I don't have to synchronize players. So there will be evening when the story move forward a lot, then days without activity. If nobody is waiting for you, that's OK. Also, when you play alone, it's OK to split the party - because here as well, nobody is waiting. So it means I don't have to force characters to stay together if they don't get along, and I can imagine more complex scenarii where multiple things happen at the same time and various characters will follow various paths.
Regarding preparation, just like regular DM work, you spent way more time in preparation than in game. Maybe a bit more, because PCs are more than just NPCs, and you need to know them well and constantly refresh your mind about who they are.
A last thing about battle : I make maps in inkscape, with tiles, and play it as a tactical game. The one thing I noticed is that I have to make the difficulty level way harder (I play twice the difficulty of the "deadly" level for a normal difficulty encounter). This is because the coordination between PCs is insane, since you play all of them. I could force on them ignorance of what the others try to do, but since I like a lot tactical games, I find it more fun to just raise the difficulty. This also means they get way more XP than usual, so I use milestone progression instead.
Oh, and another thing I found useful : I keep note files where I log what each character know about other characters. Trying to remember who knows what drove me insane, initially :)
The main difference is on the DM side, about how to build the campaign. I run the game in Faerûn, using the awesome Forgotten Realms wiki [1] to provide material. I don't try to follow everything from it exactly, but this provides a source of outside content, so that when the party reach a place, I discover much of it as well. I have also a high-res map of Faerûn that I load in inkscape to put tokens on it to show where the party is, and what there is around.
I made myself a NPC generator, based on the suggested rules in the "This is your life" chapter of Xanathar's Guide to Everything, with personal additions for commoners' life. When my party reach a place, I'll generate about twenty characters, and look at their generated lifes. Quickly, there'll be groups of characters that have similar events in their life, and imagination will take the relay to explain those similarities and produce a story for them. I change everything I want in those characters, the generated content is just a suggestion, but I think randomizing the most things possible is key to keep entertained in a solo game - that and adding outside content you discover on the go. It allows to emulate the exploration aspect of a game as a player. Plus, as a programmer, building generators/randomizers is half the fun :)
There are also difference in gaming rhythm and splitting the party. Since I play alone, I can play whenever I want, I don't have to synchronize players. So there will be evening when the story move forward a lot, then days without activity. If nobody is waiting for you, that's OK. Also, when you play alone, it's OK to split the party - because here as well, nobody is waiting. So it means I don't have to force characters to stay together if they don't get along, and I can imagine more complex scenarii where multiple things happen at the same time and various characters will follow various paths.
Regarding preparation, just like regular DM work, you spent way more time in preparation than in game. Maybe a bit more, because PCs are more than just NPCs, and you need to know them well and constantly refresh your mind about who they are.
A last thing about battle : I make maps in inkscape, with tiles, and play it as a tactical game. The one thing I noticed is that I have to make the difficulty level way harder (I play twice the difficulty of the "deadly" level for a normal difficulty encounter). This is because the coordination between PCs is insane, since you play all of them. I could force on them ignorance of what the others try to do, but since I like a lot tactical games, I find it more fun to just raise the difficulty. This also means they get way more XP than usual, so I use milestone progression instead.
[1] https://forgottenrealms.fandom.com/wiki/Main_Page