In what order should I watch Flash and Arrow TV Shows?
I've only been watching Arrow so far, and Barry Allen has just turned up. Do I need to start watching Flash episodes?
What order do I need watch these shows in?
For a more inclusive answer, (covering the other four interconnected shows as well), see http://scifi.stackexchange.com/questions/117192/what-is-the-viewing-order-for-cws-dc-shared-universe
Ideally, you should watch them in the order they aired. That is, if you want to get the most coherent story from both shows, you should watch Arrow up through the end of Season 2, then watch alternate episodes of The Flash Season 1 and Arrow Season 3. There is only one time when the shows seem to be significantly out of sync, and it won't make a whole ton of difference. In particular, watching in this order is the easiest way to guarantee not to spoil anything from either show by watching the other.
The second season of Arrow contains what is essentially a two-part pilot episode for The Flash, where a mundane Barry Allen comes to Starling City as a forensics expert; the end of that Arrow episode sets up the first episode of The Flash.
The first episodes of The Flash Season 1, and Arrow Season 3, take place at the same time, and there are cross-over cameos at the end of those episodes. Otherwise, the crossover events all seem to fall roughly in line with the order the episodes aired (e.g. crossovers that start on The Flash finish the next night on Arrow, or take place roughly between the previous and next episodes of the other show.)
So, watching in date-aired order is (almost) always going to work best for getting the entire story exactly as it was intended.
However, if watching them in air-date order is difficult (e.g. you're watching on Netflix or DVD where jumping between shows is tedious) you don't need to watch the episodes interleaved get the full story. In fact, there is at least once case where that will be a bit confusing: the timelines of the two series remain mostly in sync with each other for the first 2/3 or the season, but sometime between episodes 9 and 15, Arrow pulls ahead of Flash. If you're interested, there's a very spoilery explanation here:
So, if you prefer watching one show at a time, you really only need to pay attention to the places where the stories meet. I've put together a quick comparison of the timelines of the shows and where they cross. For the episodes in between the cross-over points, you can watch each series straight through if you want. You will miss out on a bit of Easter-Egg-level details, where the shows occasionally refer to each other's ongoing plots, but nothing central ot particularly spoilery (that I know of.)
However, you'll want to make sure you're caught up on both shows at the cross-over points, or you'll not only be confused, but probably spoil something for yourself in the process. For example, characters from Arrow reveal key aspects of Arrows's season 4 plot up to that point when they show up on Season 1 of Flash.
Flash Arrow Crossover ~~~~~ ~~~~~ ~~~~~~~~~ S01E01 <--> S03E01 Same scene appears at the end of both episodes. . . . . . . S01E04 <-- . Felicity Smoak visits Barry at some indeterminate point . . . . . . S01E08 <-- . Two-part crossover, starts on *Flash*, end on *Arrow* . --> S03E08 . . . . . S03E15 S01E18 <-- . Crossover on *Flash* between episodes 15/16 of *Arrow* . S03E16 S01E19 <-- . Crossover on *Flash* between episodes 16/17 of *Arrow* . S03E17 . . . <-- S03E19 Crossover on *Arrow* between episodes 20/21 of *Flash* . . . . . . S01E22 <--> S03E23 *Arrow* episode 23 appears to take place "during" *Flash* episode 22. S02E01 S04E01 . . . . . . S02E08 <-- . Two-part crossover, begins on *Flash*, ends . --> S04E08 next day on *Arrow*; also counts as back-door . . pilot for *Legends of Tomorrow*. NOTE: The arrows indicate the "direction" of characters crossing from one show to the other Which is usually character from *Arrow* going to *The Flash*.
I don't understand your last comment; how is *'you could just as easily watch the first 7 episodes of The Flash, then the first 7 episodes of Arrow; then watch the next episode of each; then go back to watching one show at a time.'* and *' if you want to get the most coherent story from both shows, you should watch Arrow up through the end of Season 2, then watch alternate episodes of The Flash Season 1 and Arrow Season 3.'* not mutually exclusive?
they are mutually exclusive. they are two options, one of which IMO gets you a more coherent story (since there will be occasional throw-away lines referencing each other), but the other will be far more convenient (if, e.g. you're binge-watching one series or the other) at the cost of a tiny bit of continuity.
Oh, so the 'watch alternatly' is merely for when the characters off-handedly say 'Did you hear about what happened in Central/Starling City...?'
mostly. Even when I watch several episodes on DVR in a row I alternate, just in case :) but in hindsight you won't miss out on anything "major". Up through ~episode 16ish, the timelines seem to be in sync, and watching them that way just "feels" better to me.
"Watching the episodes in air order" broke down over the last few weeks - IIRC the last crossover had pretty big things going down in Arrow that were just ignored in Flash. Not that there's a *better* order to watch them in, just that it doesn't always work.