As an amateur furniture restorer it is unlikely that you would start on a genuine antique piece. Too expensive, if it went wrong. More important, you could spoil it through inexperience and in fact reduce it's value considerably. Better to have a look around shops that deal at the cheaper end of the market, they will most likely have the odd chair or table to get you going at a realistic price. If the price seems a little high, bargain with the dealer. He will want a sale and will usually give around 10% discount. Offer cash and you will have a better chance. Trying to pay by credit card won't get you any bargains.
Looking around open-air markets and of course car boot fairs may turn up something. You will have plenty of time to have a good look at the piece and if they are regular holders they will sometimes look out for pieces for you, once they get to know what you are looking for.
Auctions, are of course the main sources of furniture. You could be bidding against dealers but still have a good chance, as you won't be looking for a profit on top of the price. Care should be taken not to pay more than the market price, so get to know your prices.
The auction catalogue will give a description of an item, along with an estimated price and will sometimes have the letters A/F (at fault) against it. Something worth looking at as it will need some work doing to it. Auctions can be daunting places to buy, but can also be very exciting as the bids go up. If it is too much for you, why not leave a commission bid on the item. The auctioneer will act for you up to the maximum price you wish to pay. Add on to the final bid price, between ten to fifteen percent buyers' premium, depending on the auction house.
The more you look, the more you will learn.