a) Picking a Great Boss
=> This option does not tell much really. In games, the term "boss" refers to a tough enemy, who is hard to kill and requires tactics to beat. So of course if the "boss" is easy to kill, then it is not boss at all.
Actually, although most bosses are "Hero" units, it matters really little what their level is or how many points they have in each attribute, nor what attribute is the main one - it really matters little, since attributes change/improve things, which you can set without changing attributes => e.g. agility increases attack speed and armor - this can be easily set in other fields.
So yeah, those attributes and levels matter very little, unless they are "core" mechanic of the boss.
b) Surrounding of the boss
=> Again, this doesn't tell much and is way too general. What is "good surrounding"? This would require examples of what you think that "good surroundings" are, etc.
"Most bosses are found in dungeons and forests, some are in caves, cities, buildings etc... The Terrain ofcourse! The terrain must fit in to the genre of the boss, either dungeon or caves or forests or whatever! DEPENDING ON YOU!" - nope, that doesn't matter. You can make a water elemental-type boss in a beehive and it will still make sense if you do it right.
While that may be exaggerated, let's say that the boss is an Wind Elemental who attacks some city - the city may still be undamaged and the boss certainly isn't in "his element", but it still makes sense that he is in there.
Of course, having a Fire elemental Boss in sea doesn't make much sense right.
Also writing this little for where boss should be and finishing it with "depending on you" is not really good for tutorial.
c) Help!!
=> If you can constantly heal and regen mana using items that spawn the whole time when fighting boss, then it is not boss at all, only a unit that has lot of health and takes a lot of time to put down, since those items will *remove* the danger of being hit by abilities, not conserving your mana for heals, etc.
Again, this lacks any of your own looks at the matter, like when *you* would suggest to use it, some examples, etc.
A paragraph, which can be summarized in "we don't want boss to kill players, so we use this trigger" is really telling nothing.
d) Opening and Closing
=> This depends on what kind of map you are playing. Is it a dungeon-type map, where you aim to kill bosses? Is it RPG-type map? Is is single player or multi player?
In case of multiplayer map, it may not be the best idea to have long cinematic scenes, as it is rather difficult to "skip" those cinematic correctly, not to mention players will be interested in seeing it for only the first two times, then they'll grow bored of it... unless you aim for your map to be played only once or twice, which would be really sad.
And also, cinematic scenes should be used only for certain bosses - like the last one, who explains the "twist" of the story/reveals his true intentions, etc., or the first one, who actually starts the story.
If I have to wait between each boss and listen to his 5 minute speech, then I'd rather shut down my WC3 and go play other games :/
e) Custom Skills
=> well, duh, custom skills are base for everything. I don't want to play 10 maps, each created by different author, and all those maps have heroes and bosses who use same skills, but have different unit models. That would be really boring.
Apart from writing that those skills are hard to make, some are made through triggers and other are just modified base spells, this paragraph tells nothing at all and it doesn't mention anything related to boss and his potential custom skills.
This paragraph should be focused on what type of abilities boss should have, what affinity those abilities are supposed to have, etc.
This paragraph explains nothing of the above.