My First Platinum Solo!

Solid advice given by everyone else already. Remember, surviving 11 waves is priority number one. This isn't a speed run. Choose a setup you feel is most likely to get you back on the shuttle. Giant and White are the best map options. Both maps provide cover/RHA just about everywhere without you having to traverse open space when/if you need to retreat.
A couple of thing needs to be added though: Soloing is a different beast, requiring patience and a somewhat stable mental health  . Both will most likely be put to the test but a failure doesn't mean it's impossible. It just means more grinding. If the satisfaction of succes is worth the grind, go for it.

(venom)

So, my two cents:

Giant is probably the easiest map for a first plat solo, but as others have noted it also takes quite a bit longer than other maps, which can be its own kind of difficulty: takes more stamina and concentration to complete a solo that takes, say, an hour, vs one that takes 30-45 mins. Plus, Giant is a real pain for grenade kits thanks to the single grenade ammo boxes and how big the map is. 

So, if you're familiar with White, I'd actually recommend starting with White. Especially if you plan on playing a grenade kit. And on that note, I'd recommend considering a grenade kit, because grenades are OP and so are several of the kits that use them: the BatSol, Krogan Soldier, QME, VorchaSent, Drellgod/Drelldept, etc. all dominate on White. Batarian and Krogan soldiers are less squishy, but also less mobile, while the QME, Vorcha, or Drell kits are squishy but highly mobile. So that's sort of a personal style/preference question. 

Other beginner-friendly kits for Plat solos are the AIU and the TGI (probably the two most EZ-mode kits in the game), Flamer GTS, the Valkyrie, or really any Infiltrator (DI and GI probably the best of the group). The Krogan and Batarian Vanguards can be fairly EZ-mode, but you obviously have to be EXTREMELY careful and judicious about Biotic Charging with so many sync-kill enemies on Plat. Destroyer is also a solid kit, with awesome DPS and good survivability, but also quite immobile with no dodge (assuming you're using DM) and a slow sprint. 

So that covers maps and kits, the last piece is choice of weaponry: obviously the best weapon for plat solos is the Venom, but I know not everyone enjoys or is as good with it, so the Hurricane/Acolyte combo is a good substitute if you don't mind switching weapons. Can also do Hurricane/Scorpion, if you prefer the Scorpion to the Acolyte as your anti-Phantom gun. But whatever your loadout, you DO need a plan for dealing with Phantoms- a good way to practice for a plat solo is to do Gold Cerberus solos, so you get used to dealing with Phantoms on a higher difficulty solo. And if your aim is good, the BW or Javelin is also perfectly viable on Plat. You want a weapon that is not only effective, but that you're comfortable with (and, ideally, one you enjoy, since this is a game and the purpose is ultimately to have fun).

And then, of course, there is the Reegar: it sucks to use, but its effectiveness is undeniable. But you have to weigh the pros/cons of having such a short range weapon (and with its weight, you probably can't have a secondary unless you're playing a kit/build that doesn't care about cooldowns, like an Infiltrator). It synergizes particularly well with Vanguards, the AIU, or the Valkyrie.

And watching videos of other plat solos is invaluable and always a good idea- if you can, find videos of people soloing the map/faction you intend to solo yourself, and ideally with a similar kit/build/loadout as well. Pay particular attention to how they move about the map, where the RHA spots, chokepoints, and spawns are, and how they deal with objectives.

Another good idea is to do a Gold solo of the map/faction and with the same kit/build/weapon you intend to use for a Plat solo; so if you're thinking of trying Plat/Cerberus/White with e.g. Venom Valkyrie, do a few Gold/Cerb/White solos with that kit and weapon. One of the most important things for plat solos is having an intuitive sense of where the spawns are and which directions the enemies are coming from, and those tend to be more or less the same on Gold as on Plat.

I probably did half a hundred Gold solos before trying my first Plat solo, and I think that really helped flatten the learning curve for me when I finally got up the courage to try a Plat solo.

Yeah I'll admit that I did quite few Geth/Glacier/Gold solos with the Kroguard in my early soloing days... gotta start somewhere, after all!

(I'll also admit that, shamefully, I used the Reegar quite a bit in those early days- Reegar AIU, Reegar Kroguard, Reegar Jugg, etc)  

Excellent tips, i do play white a lot so I am comfortable with that map. Though on lower levels i usually just camp at position two and deal with it that way but a 2nd or third spot will be essential for sure. Thanks for the work.

So from position 6 you are battling spawns coming from up top and the landing zone i take it?

I don't like position 6, cause I m often punished by goons hunters and phantoms coming from 5 maybe I m just not trying enough. But feels retreat from 7 is anyway easier even if attacked from behind? Or maybe it s because you can easily check your left and the respawning there.