Under GST regime exports would be considered as zero-rated supply. In case of Exports of goods to SEZ and other countries you have to charge IGST and then export.

Any person making zero rated supply (i.e. any exporter) shall be eligible to claim refund under either of the following options, namely: ––
(a) he may supply goods or services or both under bond or Letter of Undertaking, subject to such conditions, safeguards and procedure as may be prescribed, without payment of integrated tax and claim refund of unutilised input tax credit; or
(b) he may supply goods or services or both, subject to such conditions, safeguards and procedure as may be prescribed, on payment of integrated tax and claim refund of such tax paid on goods or services or both supplied, in accordance with the provisions of section 54 (Refunds) of the Central Goods and Services Tax Act or the rules made there under (i.e Refund Rules 2017).
For the option (a),procedure to file refund has been outlined in the Refund Rules under GST. The exporter claiming refund of IGST will file an application electronically through the Common Portal, either directly or through a Facilitation Centre notified by the GST Commissioner. The application shall be accompanied by documentary evidences as prescribed in the said rules.Application for refund shall be filed only after the export manifest or an export report, as the case may be, is delivered under section 41 of the Customs Act, 1962 in respect of such goods.
For the option (b),the shipping bill filed by an exporter shall be deemed to be an application for refund of integrated tax paid on the goods exported out of India and such application shall be deemed to have been filed only when the person in charge of the conveyance carrying the export goods duly files an export manifest or an export report covering the number and the date of shipping bills or bills of export and the applicant has furnished a valid return.

For Bond and Bank Guarantee contact your CA and your banker.