A very common question I’ve seen on social media is “do I need to send save the dates?”.
I think this is a personal decision for a couple, but the main considerations are budget, design and time. Is it an expense you can do without? Or perhaps make something digitally and send via WhatsApp or Facebook? Could you design it yourself to save cost, or can you find a good template online? How long is your engagement? Do you need to do save the dates? 
We decided against them. Our engagement was only a year, we told our nearest and dearest when we set the date and booked the venue, and then others heard by word of mouth, so it saved us time and money in doing them. 
I completely understand them if you’re having a destination wedding or a longer engagement as it makes sense to give your guests a year plus notice to book flights and hotels. 
Another common question which flies around social media is “when do I send invites?” Again, I feel like this is a personal choice, but also depends on when your venue needs final numbers by. If you haven’t sent save the dates, probably sooner rather than later. Plus if guests need to book accomodation, earlier is probably better, especially if your venue has limited rooms or limited hotels nearby. 
Another thing to consider is how many people you’ve invited. If you have minimum numbers, and people pull out, I’m sure you’d want to fill the spaces. Sending invites earlier to capture drop outs is a good idea, as it will then give you time to upgrade evening guests before the venue need your numbers. Plus, you’d need time to prepare a table plan before you send final numbers to your venue, so need RSVPs back before then! 
Finally, what format is acceptable for invites and RSVPs? A growing number of brides to be are heading digital and creating a wedding website for collecting RSVPs, but still sending a paper invitation. Don’t get me wrong, the traditional paper invites are stunning, with so many options for designs, materials and packaging. But all this comes with a cost, plus postage, plus postage for RSVP envelopes. Moving digital cuts the RSVP costs down to nil, and then guests can still keep beautiful invites as a keepsake, without having to remember to post that RSVP! 
We decided to go completely digital with invites (except for a few grandparents and uncles!), and sent via WhatsApp or Facebook Messenger. Our wedding website gave more details and allowed guests to RSVP plus give their menu choice too. This brought our invite cost down to nothing, the website was free and better still, we don’t have to write down or collect menu choices ourselves as the website does it for us, with a download of a CSV! 
In summary, do what makes you happy and reflects you as a couple! Take into consideration your guests, and how tech-savvy they are, but also whether they’d want to treasure your invite.