Every time you send a Bitcoin transaction, there's a fee to be paid to the miners. Miners naturally prefer transactions with higher fees. So the more you pay, the faster your transaction is confirmed. The optimal fee depends on the size of the transaction, not the value. At the time of writing, TradeBlock recommended a 54 sat/B fee size.
Example: Tom has 10 BTC in a single BTC address. He sends 1 BTC to Alice. This transaction has 1 input (10 BTC) and 2 outputs (1 BTC to Alice and 9 BTC back to Tom). In this case, the optimal fee size will be on the lower end. Bill has received 10 transactions of 0.01 BTC each. Now he sends 0.1 BTC to Alice. The optimal fee for this transaction is much higher than Tom's transaction because there's a lot more data here: 10 inputs and 1 output.
Under normal circumstances, the bitcoin fees are very reasonable. If you use an optimal fee size, you can expect your transaction to be included in the next block (in about 10 minutes). Even if you lowball the fee, you could still expect to see the transaction confirmed within a few hours. Unfortunately, on many occasions during the last few months, there has been a group of malicious actors spamming the bitcoin mempool with a significant number of low-fee transactions. This affects the regular transactions; now they have to pay a higher fee to get confirmed. Roger Ver and his Bcash puppets seem to think that by attacking Bitcoin they can pump their trashy project. They have halted their attacks for now. However, just in case they start again; here are 4 ways to speed up your bitcoin transactions:
Free Bitcoin Transaction Accelerator Services
Lately, a couple of new websites have launched that speed up your bitcoin transaction if you enter the transaction ID. Most of them also offer a paid service, but I have been delighted with the free product. So no need to spend any money on this. Here are a few recommended acceleration services: choose the free option and simply copy/paste your transaction ID:
Replace-By-Fee
This option is only available in some wallets (in Electrum and Ledger, for example). As the name suggests, the wallet replaces the fee in the original transaction with a higher fee to speed up confirmation time.
Child Pays For Parent
This can be an expensive but effective solution for an unconfirmed transaction: copy/paste your wallet receive address in your wallet send tab. Now select the maximum amount and highest fee and hit 'send'. This effectively sends the full balance of your wallet back to yourself. If the fee on this transaction is a high enough, it helps confirm all previous unconfirmed out-going transactions in your wallet.
Be Patient
Unless you are in a hurry, the best approach is just to wait. The transaction will confirm eventually.
Picture Credits: 1. Uroš Jovičić, 2 - 3. Igor Ovsyannykov, 4. Cody Black