First of all, never automate. The AI is called the
artificial
idiot for a reason.
At the beginning of the game I usually do mine, road, then move, then mine, then road, and so on. Sometimes I just build a road in advance to a resource, then double back to build a mine or irrigate, then retake the forward path to reach the resource or build a city.
The equation might change slightly with agricultural or industrious civs.
Deserts are usually wastelands but in my current game I'm in the early middle ages, playing with the Celts, and have six highly-productive cities located on pure desert. This is because irrigated desert tiles produce one extra food for agricultural civs, so every irrigated desert tile with a road is just as productive as a grassland tile with a mine and a road. So agricultural civs can expand into deserts earlier and this should not be neglected.
With industrious civs you might actually have idle capacity occasionally because something takes 1.5 turns to make so you either set one worker to do it and take two turns (wasting half a turn's worth of work) or use two workers and save yourself a turn but also waste half a turn's worth of work. Which is where captured workers come in.
Of course you have to also send out workers to just build up your trade network (foreign trade can really be profitable if you know how to handle it). It's sometimes best to just keep two or three separate stacks of workers.
Also, remember that worker efficiency, unlike city productivity, does not vary with distance from the capital or any (lack of) city improvements, so it is perfectly fine to build outlying cities near flood plains or grassland, irrigate the whole lot and have them churn out workers while other cities specialise in building units and improvements… and, if you can afford it
and thoil i.e. justify it, wonders.
Those were general recommendations.
Now, as for roads themselves… every time you move onto/off a tile without a road it takes 1 entire MP, so you'd better maximise worker efficiency by building roads as you go along.
Suppose you have a group of three workers, all of them on one tile. If you move them all to the next tile (flatland) that takes one turn, then you build a road, which is another turn, then you repeat the process for the other two adjacent tiles, that's six turns just to build roads for three flatland tiles. If instead you send each of the three workers to a different tile you'll have all three tiles with roads on them in just four turns. So unless you need to power through mountains or hills you'd better not concentrate workers for roadbuilding.
With forests I recommend not chopping them down in the first two ages at least because tiles producing 2 shields apiece are rather rare, and also they can be really helpful holding back invaders. Remember, the AI will not move an SOD into your territory if they cannot dominate terrain, and just this past week I've successfully tested it: I averted invasions by going back three or four turns and moving a stack of workers (along railroads) to rapidly erect barricades and/or plant forests - the AI never invaded or declared war. Oh, and the AI cannot handle artillery - they
will move a stack of 40-odd modern armour units even if there's a stack of 60-odd artillery units waiting just behind a double line of barricades to shred them into pieces. Or just a stack of 4× infantry, 1 musketman and 1 guerilla guarding two dozen Cavalry straight into said double line of barricades with 60-odd artillery units stacked behind them.
But I digress. Back to the workers! As I was saying, better not chop down forests because of the two-shield-per-tile yield, but jungle and marsh should definitely be cleared first and have a road built second. Just think: on cleared flatland it requires three turns to build a road but on jungles it takes 9. If it's within city radius, first clear, then build road. You'll also reduce the risk of disease along the way. If it's outside city radius, just build a road: you will save turns and it will be an obstacle, again, for future invaders.
Resources are distributed at the start of the game, so they will show up regardless of whether you've terraformed the tile or not.
I hope the above wall of text is not too dense. Feel free to ask questions.