In my early stages I started by cutting out bread, rice, potatoes, pasta and sweet things to see how I got on.
Bread ideas: a ham sandwich, two slices of ham with Philadelphia between them to stick them together
Celery filled with peanut or almond butter or Philly
Otherwise just eat the sandwich filling without the bread, ie some ham slices, some cheese.
No more jam, honey, Nutella etc!
Pasta suggestions: I often cook button mushrooms and use them instead of the pasta. Just cover them in the same pasta sauce the rest of the family is having.
Rice: I bought a handled grater (I'll post a link) and make cauliflower and/or broccoli rice multiple times a week. You can buy premade cauliflower rice which is ok but it's much nicer fresh. I shallow fry it in butter or olive oil and sometimes mix in some spices. I'll never go back to normal rice.
Potatoes: this is quite hard to replace but sometimes I just mash potatoes and cauliflower together so it's half and half.
Sweet things: I now pretty much only eat a square or two of dark chocolate (70%+) but it's hard to start with.
Other tips: full fat Greek yoghurt with 4 seed mix makes a great and very easy breakfast. Feels a bit like granola and yoghurt but no oats or sugar.
Eggs. Eggs. And more eggs.
Handful of plain nuts when you're struggling with munchies/need energy.
You should eat lots and lots of salad/green veg. At least one meal per day is a salad when I'm lose carbing but they are beautiful salads: some nuts, meat, all the trimmings really. Or salad on the side of a juicy steak or some lovely fish.
Once you get more into it and enthusiastic, you can start to look properly at low carb high fat stuff. You soon begin to learn to check anything for carb content. Essentially if something is in a packet check the carbs per 100g. You want it to be 5 or less per 100g for low carbing, but 10g or less per 100g is ok in moderation. For Keto you're looking to consume roughly 25g or less over a whole day.
Once you've got a bit used to it you can learn which fruit, veg, pulses etc you should be avoiding. Off the top of my head, most fruit should be avoided other than berries in small amounts. Green veg is mostly ok but sweet coloured veg like carrots, sweetcorn or sweet potato is a no. Oats, lentils, beans etc should be avoided. You can make things tasty and satisfying with butter, cheese etc.
I lost 2.5 stone low carbing but more than that it forced me to reconsider my relationship to food and nutrition. I now eat kind of normal food but much more thoughtfully and some habits have stuck - loads of salad for example. I also realised that I was bloated and uncomfortable a lot of the time and that went away.