First, it's 全然おk to make a bunch of mistakes. Been there, done that. Humans make mistakes. It's what we do. So don't stress too much about getting it perfect.
Rather than Anki-ing the hell out of it, go find a human to practice with if you can. Build those muscle memories, and train yourself to say the right set phrases with someone who can tell you immediately when you screw up.
When you're in a conversation, remember to say, "はい、はい," "ええ、ええ," or "うん、うん," at close intervals to avoid creeping the hell out of your Japanese counterpart. You're not agreeing, you're just acknowledging that you've safely understood what they've said. Pick one according to politeness level. Don't say "うん、うん," to your boss.
Other conversational interjections: if something bad happened, 大変ですね, or 残念ですね. If something good happened, いいですね, or if a bad situation was prevented, よかったですね. Or a simple そうですね for variety. If it's surprising, そうですか? It's really the same as having a conversation in polite English-- if your friend is talking to you, and stuff happened to them, you might say something as an indicator of surprise or sympathy. This is the same deal. Pick words accordingly, or just はい、はい if you're not sure.
Find a good filler word for saying nothing when you're struggling to find a word to say in conversation. "あの、えっと、んとね、そうですね、まぁー" words like that sprinkled here and there (but not too much) can help you in a "Oh crap, what was that word? I need to fill this awkward silence for 2-3 seconds while I remember it!" kind of way.
んですが is really useful. 予約したいんですが… "I'd like to make a reservation (so please help me!)" 予約がありますが… or 予約があるの(ん)ですが… "I've got a reservation, but (I need help with getting my room, front desk person, so can you help me?)" I'll admit I'm a little fuzzy on the grammar details on these two. Might want to look them up. But those save my butt a lot, and nobody seems to throw things at me, so good enough for me.
A few more:
Generally, "お願いします、すみません、__をください" are your best buds. They will get you surprisingly far. すみません is something you can yell in a restaurant to get a waiter's attention. This is important, because once you order, they're usually done with you after you get your food. If you want more, すみません!
ちょっとよろしいでしょうか? Is now a good time (to deal with the problem I'm going to ask you for help with)? (Polite) This is great in デパート, デパチカ, anywhere you need to bother a salesperson or guide to explain stuff to you.
お時間ありますか? Do you have time (to deal with me?)
わざわざすみません。 Thanks for going to all the trouble to help me out.
For taxis, "___までお願いします。" <--- This saved my butt a lot too, especially when I was in a hurry.
Two books:
The Ultimate Japanese Phrasebook (ISBN: 978-4-7700-3100-6) $25US. The scope is a little overbroad IMO, it goes from getting off the plane to getting hitched to your kids going to college. I'd think you would go take some classes at *some* point inbetween, but who am I to judge? At any rate, check it out in a library first.
The Original Point and Speak Phrasebook 9 Japanese Food (ISBN: 978-4-7958-3873-4) 1500 yen. All about food, table manners, tea, regional specialties, etc., in EN and JP. You can just point at stuff if you're totally lost. Damn book makes me hungry.
Edited: 2015-09-15, 10:34 am