I do not go near Preston or near Sancturay, because Preston obviously hired a settler (she should stand guard and was extra equipped for this) to harass me 
That said: Simply do the quests he gives you, but do not hand them in. Of they have a timeout, then they will auto complete after the timeout (including the XP). But as long as you have 3 quests open you should not receive more. Also most of these quest have a very long timeout or even no timeout. Delay them as you wish. When you have more of these quests in your list you will not receive new quests.
Spoiler One other thing: At the start of the game you receive quests, or demands to build certain things. First you should build beds, water and food in Sanctuary, then you are asked to build some defenses. This is sort of a tutorial, and there are enough resources to build this all without problems. For defense - do not build MG turrets too early - its not necessary. Build several defense posts, especially at the bridges in Sanctuary. One defender can do 3 posts, and every post adds 2 defense. So you can have 6 defense per defender, if every defender has 3 posts to guard. (The posts should be not too far apart).
You also receive at least one, probably more quests to open new settlements. The problem with this is, that it is random, with the exception of Tenpines and the Drive In Cinema. These come always first. Often the Sunshine Coop is also in this list. You can open them, but its hard, not to open them but to built them up. And then often comes a settlement far in the south, which you definitely do not wish to open, since you cannot defend it and often it misses build materials too. So carefully and slow build up settlements in the north, and ignore quests for settlements further south.
Most quests asking you to open a new settlement call for you to go to the settlement, where the settler will give you a quest. Some of these quests are timed quests. But as long as you do not go to the settlement and talk with the settlers, the quest seems to be not started. I have one ignored with good reason and nothing happened, it sits there. Also do not open settlements yourself. You can do that, but it leads to one settlement more you have to maintain, and this can be hard in the beginning, when you have not enough money and not the right perks.
The thing with the settlements is, that you should plan what to open. If you have 4 settlements (including Sanctuary) you will receive a quest from Preston which you also will want to do later.
My experience is so, that I almost never do such quests immediately, and now I avoid Sanctuary and do not hand in quests already done, so I receive no new quests. If you have 6-8 settlements in mid game this is enough. You can build an maintain them well.
Another hint: Think deeply before building a settlement beacon! One of the starting quests requires to build one. The other quest do not. As long as you only build buildings, defenses and beds no settler will come! And if you have a small settlement but no beacon, it will not grow. At the beginning and into the mid game you only need one settlement with a beacon. If you want settlers in other settlements, simply send (in build mode) one of the unassigned settlers to this settlement. If all your settlements have beacons they will grow up to the maximum, without regards of the number of beds/food/water! This strains your resources, If you already have a beacon, store it in the workshop. (No need to scrap it, but switching it off does not work correctly).
If you want to build up, start slow, and develop your settlements.
Concerning attacks: Having only the original settlers there (2 or 3) is not good. There is for example a farm, with 3 people, which requires a small quest to join. If you do this, build defense stations and send one or two additional settlers from a bigger settlement to the farm, to server as guards. This way it is much easier to defend and it also works better with the crops, since the original farmers will be needed to tend the crops.
» Sat Jan 16, 2016 12:00 pm 
